vtu belgavi, karnataka notes

1. PREPARED BY
SHIVKUMAR M H [SONOFGOD]
M.E(UVCE),AMIE
ASSISTANT PROFESSOR AND HIGHWAY ENGINEER
EWIT,BANGALORE

2. UNIT - 7
TRAFFIC REGULATION AND CONTROL: Driver, vehicle and road controls –
Traffic regulations – one way – Traffic markings, Traffic signs, Traffic signals – Vehicle
actuated and synchronized signals – Signals co-ordination. Webster’s method of signal
design, IRC method, traffic rotary elements and designs, traffic operation – Street lighting,
Road side furniture, Relevant problems on above.
10 hr
EXAM QUESTIONS
1. Describe main functions of traffic control devices
2. Advantages and dis advantages of one way street
3. Mention the general principles to be observed during installation of traffic signs.
4. Write short notes on: i) Mandatory signs. ii) Informatory signs. (iii) traffic regulation
5. Explain 3 warning signs and regulatory with neat sketches
6. Advantages and dis advantages of traffic sign
7. Mention different types of traffic signals. Explain an one of them
8. Advantages and dis advantages of traffic signals
9. Highlight functions of different types of signals

3. 10. explain phasing of traffic signals
11. describe Webster method of signal design
12. difference b/w actuated signal and synchronized signal
13. discuss briefly fixed signal and vehicle actuated signals
14. Write a note on signal co-ordination and traffic actuated signals
15. Differentiate between traffic signs and signals under what circumstances they are used.
16. Write short notes on: Rotary intersection, what is rotary, advantages and dis advantages,
sketch and indicate various design elements of rotary, enumerate design factors of rotary
17. Explain briefly importance of street lighting and road arboriculture
18. explain the design factors of highway lighting
19. indicate and explain how spacing of street lighting is decided
20. Explain briefly importance of road arboriculture

4. TRAFFIC REGULATION AND CONTROL
 In order to have safe traffic on roads, it is desirable to impose adequate traffic
regulations and traffic control with the help of standard traffic control devices.
 The traffic regulations and control are implemented with the help of suitable
regulatory signs, signals, marking, traffic islands and other devices.
The various regulations imposed through the traffic control devices should fulfill the
requirements such as:
(i) Clear visibility during the day and night
(ii) Easy to recognize and understand
(iii) Sufficient time for the driver driving at the design speed or within the legal speed
limit to react and follow the regulation.
(iv) To ensure safety in general.
Traffic regulations and laws cover the following four phase.
- Driver controls
- Vehicle controls
- Traffic flow regulations
- General controls

5. REGULATIONS AND CONTROLS ON DRIVERS
 The controls on drivers include eligibility for driving motor vehicles, issue of
driving license and other regulations on the drivers during the act of driving.
 As per the Motor Vehicle Act, the minimum age for getting a driving license to drive
a non-geared two-wheeler is 16 years and the minimum age for driving a geared
two-wheeler or a four wheeler is 18 years.
 Driving a motor vehicle without a valid driving license is an offence.
 Before the issue of driving license for a specified category of vehicle, one has to
undergo specified tests.
 The driver is expected to demonstrate his ability to drive the vehicle safely and he
should be conversant with the motor vehicle rules and regulations.
 Separate requirements and tests have been specified for driving different categories
of motor vehicles such as two-wheeler automobiles, light motor vehicles, public
transport vehicles, heavy commercial vehicles, etc.
 There are regulations prohibiting driving under the influence of alcohol or ‘drunken
driving’.
 Dangerous driving including exceeding the specified speed limits, etc., which may
render a driver to pay specified penalty or to suspend the driving license for a
specified period or to permanently disqualify from driving a vehicle in the country.
 The Regional Transport Officer has the powers to endorse upon the driving license
the particulars of the traffic violations and when the number and severity of the
violations exceed the permissible limit, the license can be suspended or even
cancelled.

6. REGULATIONS AND CONTROLS ON VEHICLES
 Regulations and controls on vehicles include vehicle registration, requirements of
equipment and accessories of motor vehicles, maximum permissible dimensions and
weight, vehicle fitness, inspections, etc.
 The registration is essential for any new motor vehicle.
 The information about the details of the vehicle such as the type, make, capacity of
engine, manufacture’s serial number, details of the owner, license plate number, etc.
are registered in the transport department and police records.
 There are different specifications for public transport vehicles, hired vehicles and
private vehicles for displaying the registration number.
 For example private vehicles have to display the registration numbers of specified
size letters and numerals written in black colour on plate with white back-ground.
 The specified colour of the registration plate is yellow for public transport vehicles
including hired vehicles.
 The regulation covers the length, width, height, type and condition of tyres,
maximum weights of commercial vehicles seating arrangements and number of
seats in public service vehicles, lamps and signaling appliances, emission, noise, use
of horn, speed governors , safety glasses, etc.
 At least a third party insurance policy is mandatory for all vehicles.

7. GENERAL REGULATIONS AND CONTROLS
 Some other general regulations and provisions are made.
 They include reporting of accidents, recording and disposing traffic violation cases,
etc.
IMPLEMENTATION OF REGULATIONS
 The traffic regulations have been enacted and implemented in India with the help of
the Motor Vehicle Act of 1939, The revised Motor Vehicle Act of 1988.
 These have covered various traffic regulatory measures in three major phases,
namely control on the
(i) drivers
(ii) vehicle ownership and
(iii) vehicle operation on roads and in traffic stream.
 The various items covered are issue of driving license, registration of vehicles,
transfer of ownerships, distinction between private and public vehicles, transport
authorities and inter-state commission, limits of speed, weight, restrictions on
parking and halting places, vehicle insurance and fees, signs, signals and general
provisions for punishment of violations and offences.
 Some of the most common traffic flow regulations such as
(i) one-way regulation and (ii) turning restrictions at junctions
 Various other regulations such as Stop, Speed limit, Restrictions on overtaking,
parking, stopping, etc. are implemented by appropriate regulatory signs.

8. ONE-WAY STREETS
General requirements for introduction of one-way streets
 In congested streets, one of the methods to reduce severe vehicle accidents and to ensure
smooth flow of traffic is by regulating traffic along one-way streets.
 The traffic is allowed to move only in one specified direction.
 Such regulation are possible only when there is a net-work of roads connecting two bigger
roads so that additional distance to be traversed by some vehicles through these one-way
streets is not excessive.
 As a general guideline the Indian Roads Congress suggested that due to the introduction of
one way regulation, the extra distance to be travelled does not exceed 30 percent of the
original distance.
 This is feasible only when complimentary roads are available at fairly close intervals.
 Proper care should be taken to study the pattern of the displaced traffic as a result of the
one way system.
 Installation of appropriate traffic signs and lane marking are essential before the
introduction of the one way system.
 Appropriate regulatory signs such as ‘no entry’, ‘one-way’, ‘no right turn’, ‘no left turn’
should be erected at all strategic locations, especially at the ends of the one way street and
at the meeting points of cross roads.
 These regulatory signs along with ‘supplementary regulation signs’ (blue coloured
circular sign boards) installed at appropriate locations provide advance information on
the regulatory signs ahead.
 In order to scientifically plan and introduce a one-way road system in a city, it is
desirable to first consider the existing road network as a whole and also arrange to
carryout comprehensive traffic studies in the city.

9. ADVANTAGES OF ONE-WAY ROAD SYSTEM
(i) Increase in average travel speed
(ii) More effective co-ordination of signal system
(iii) Slight increase in roadway capacity
(iv) More stream-lined movement of vehicles
(v) Reduction in severe accidents involving head-on collisions
(vi) Reduction in conflict points at un-controlled intersections at-grade, resulting in
reduction in accidents and
(vii) Improved pedestrian movement.
DISADVANTAGES OF ONE-WAY ROAD SYSTEM
(i) Increase in travel distance for majority of vehicle trips
(ii) Possible increase in fuel cost and also travel time for a small proportion of
vehicles
(iii) Possibility of violation of one-way regulation (to save extra travel distance) by
some road users in the absence of strict enforcement, resulting in additional
accidents .
(iv) Difficult for pedestrians to cross wide one-way roads-this may lead to additional
pedestrian accidents on such wide road stretches, unless appropriate measures are
taken for safe pedestrian crossing facility at identified locations

12. TRAFFIC CONTROL DEVICES
 The various aids and devices used to control, regulate and guide traffic may be
called traffic control devices.
 The general requirements of traffic control devices are:
- attention
- meaning,
- time for response and respect of road users.
 The traffic control devices installed along the road should be well within the field of
vision of the drivers who are driving their vehicles at the design speed or at legal
speed limit;
 These devices should distinctly draw the attention of the drivers and should convey
the meaning without any ambiguity.
 The location of these devices should be such that there is sufficient time for the
driver to respond and take appropriate action.
 The most common among the traffic control devices are:
(a) Traffic signs
(b) Traffic signals
(c) Road marking and
(d) Traffic islands.
 In addition, road lighting is useful in guiding traffic during night.
 It is also essential that these traffic control devices and their meaning should be
easily understood even by the road users who are not familiar with the language of
the country.

13. GENERAL FEATURES OF REGULATORY SIGNS
 Regulatory signs are also called ‘mandatory signs’.
 These signs are meant to inform the road users of certain laws, regulations and prohibitions.
 The violation of any of the regulatory signs is a legal offence and is punishable as specified.
 All regulatory/mandatory signs are circular in shape, with only two exceptions – they are,
(i) ‘Stop sign’ of octagonal shape
(ii) ‘Give way sign’ in the shape of an inverted triangle.
 Among the regulatory signs of circular shape, majority of them have a red coloured border of
width 60 mm and white colour in the interior;
 However the colour of the interior of ‘No parking’ and ‘No stopping’ signs are blue.
 Other exceptions in this category are,
(i) ‘No entry’ sign which is of circular shape, but full red in colour with a white coloured
horizontal strip of width 90 mm and
(ii) ‘Restriction ends’ sign – this sign indicates that the prohibition or other restriction imposed
by the regulatory sign ends at this spot; this is a circular sign board, white in colour with a
black diagonal strip of width 130 mm.
 The second category of regulatory/mandatory signs are intended to supplement the main set of
signs;
 These are classified under the category ‘Compulsory direction control and other signs’ – these
signs are also circular in shape, but blue in colour and white coloured arrow marks within.
 Thus the regulatory/mandatory signs may be classified under the following sub-heads:
- Stop and Give-way signs - Prohibitory signs
- No parking and No stopping signs - Speed Limit and Vehicle Control signs
- Restriction Ends sign - Compulsory direction control and other signs

15. TYPES OF REGULATORY SIGNS
STOP SIGN
 The ‘Stop sign’ is of octagonal shape and red in colour with a white border of width
60 mm.
 The stop sign is intended to stop the vehicles entering a major road from a minor or
side road, where the traffic must compulsorily come to a stop before entering in
major road;
 the stop line has to be clearly marked on the pavement and the stopped vehicle shall
proceed beyond the stop line only after ascertaining that this will not cause conflict
or danger to the traffic of the major road.
 The drivers have to understand the significance of the stop sign of octagonal shape,
even without the need no read the word ‘stop’, if it is written in any language.
 However the regulatory signs may be used in combination with a rectangular
definition plate with the word ‘STOP’ written in English and other languages as
necessary.

16. GIVE WAY SIGN’
 The ‘Give way sign’ is in the shape of an inverted triangle with its apex downwards,
has red border of width 70 mm and white interior.
 The give – way sign is used to control the vehicles on a road so as to assign right of
way to traffic on other roadways.
 This sign may also be used in combination with a definition plate.
PROHIBITORY SIGNS’
 These signs are circular in shape, white in colour with a red border and a red
diagonal line.
 ‘Prohibitory Signs’ are meant to prohibit certain traffic movements or entry of
certain vehicle class.
 The different types of prohibitions are shown symbolically in black colour.
 The different types of signs under this category include ‘
Ex - One-way’,
‘Motor Vehicles Prohibited’,
‘No entry’, ‘U-turn, Right turn or Left or turn Prohibited’
Overtaking Prohibited’, ‘Horn Prohibited’, etc.

17. NO PARKING’ SIGN
 The No Stopping/Standing sign is circular in shape with blue back ground, red border and
two oblique red bars at 45 degrees and right angle to each other.
 No Parking’ sign is meant to prohibit parking of vehicles at that place, the definition plate
may indicate the parking restriction with respect to days, distance, etc.
SPEED LIMIT’ SIGNS
 These signs are circular in shape and have white back ground, red border and black
numerals indicating the speed limit.
 ‘Speed Limit’ signs are meant to restrict the speed of all or certain classes of vehicles on a
particular stretch of a road.
 The ‘Vehicle Control’ signs are also similar to speed limit signs with black symbols
instead of the numerals.
 The common controls are ‘Width Limit’, ‘Height Limit’, ‘Length Limit’, ‘Load Limit’ and
‘Axle Load Limit’.
RESTRICTION ENDS’ SIGN
 These signs are also circular with a white back ground and a broad diagonal black band at
45 degrees.
 ‘Restriction Ends’ sign indicates the point at which all prohibitions notified by prohibitory
signs for moving vehicles cease to apply from that point.
 Some of the regulatory/mandatory signs standardized by the Indian Roads Congress are shown
in Fig. 5.23.

19. WARNING SIGNS
 The warning signs are in the shape of equilateral triangle with its apex pointing
upwards, they have a white back ground, red border and black symbols
 ‘Warning Signs’ or ‘Cautionary Signs’ are used to warn the road users of certain
hazardous conditions that exist on or adjacent to the roadway.
 The warning signs are to be located at sufficient distance in advance of the hazard
warned against;
 These distances are to be based on the design speed/legal speed limit of the road
stretch.
 The commonly used warning signs are, ‘Sharp Curve’, ‘Right Hand/Left Hand
Curve’, ‘Hair Pin Bend – Left/Right’, ‘Reverse Bend – Left/Right’, ‘Steep
Ascent/Descent’,’, ‘Narrow Bridge/Road Ahead’, ‘Gap in Median’, ‘Slippery Road’,
‘Cycle Crossing’, ‘Pedestrian Crossing’, ‘School Zone’, ‘Men at Work’, ‘Cross Road’
‘Side Road’, ‘T-Intersection’, ‘Y-Intersection’, ‘Major Road Ahead’, ‘Round About
Ahead’, ‘Dangerous Dip’, ‘Hump’, ‘Rough Road’, ‘Barrier Ahead’, ‘Unguarded
Railway Crossing’, ‘Guarded Railway Crossing’, ‘Falling Rock’, etc.
 Some of these warning signs are shown in Fig. 5.25.

21. INFORMATORY SIGNS
 The ‘Informatory Signs’ are rectangular in shape.
 These signs are used to guide the road users along routes, inform them of
destination and the distance, thus providing with information to make travel easier,
safe and pleasant
 The colours chosen for informatory or guide signs depend on the classification of
the road.
 For National Highways and State Highways, the informatory signs shall be of green
back-ground with the borders, and word messages in white colour.
 For all other categories of roads such as MDR, ODR and VR these signs shall have
white back-ground with borders and word messages in black colour.
 The information signs are grouped under the following sub-heads:
(i) Direction and Place Identification signs
(ii) Facility Information signs
(iii) Other Useful Information signs
(iv) Parking Signs
(v) Flood Gauge

22. .
The ‘Direction Signs’ and ‘Place Identification Signs
 The ‘Direction Signs’ and ‘Place Identification Signs’ are rectangular in shape with
the longer side horizontal.
 The signs of this group include ‘Destination Signs’, ‘Direction Signs’,‘Route Marker
Signs’ and ‘Place Identification Signs’.
 Fig. 5.26 shows a typical informatory sign.
The facility Information signs
 The facility Information signs are rectangular with blue back ground and
white/black letters/symbols.
 These signs indicate facilities such as ‘Public Telephone’, Petrol Pump’, ‘Hospital’,
‘First Aid Post’, ‘Eating Place’, ‘Resting Place’, etc.
Flood Gauge
 ‘Flood Gauge Sign’ should be installed at all causeways and submersible bridges or
culverts to the road users the height of the flood above road level.

24. GENERAL PRINCIPLE TO BE OBSERVED DURING INSTALLATION OF
TRAFFIC SIGNS.
1. The sign should be placed such that they could be seen and recognized by the road
users easily and in time.
2. The transverse location of the signs may be such that in the case of roads with kerbs,
the edge of the sign adjacent to the road is not less than 0.6m away from the edge of
the kerb.
3. The transverse location of the sign on roads without kerbs the nearest edge may be
2.0 to 3.0 m from the edge of the carriage way.
4. The signs should be mounted on sign posts painted alternately with 25 cm black and
white bands.
5. The size, shape, colour code and the symbols used and the location of the signs should
be as specified under each category.
6. The reverse side of all the sign plates should be painted gray.

25. TRAFFIC SIGNALS
OBJECTS OF TRAFFIC SIGNALS
 At intersections where there are a large number of crossing and right-turn traffic, there
possibility of several accidents as there cannot be orderly movements.
 On cross roads with two-lane two-way traffic, there are 16 crossing conflicts as illustrated in
Fig. 5.20.
 The problem of such conflicts at the intersections gains more significance as the traffic
volume increases.
 In such situations the earlier practice has been to control the traffic with the help of
traffic police who stops the vehicles on one of the roads alternately and allows the traffic
stream of the other road to cross or take right turn.
 Thus the crossing streams of traffic flow are separated by ‘time-segregation’.
 In bigger cities, a large number of police personnel are required simultaneously to
control the traffic during peak hours at most of the junctions with heavy traffic flow.
 Therefore traffic signals are made use of to perform this function of traffic control at
road intersections.
 Traffic signals are automatic traffic control devices which could alternately direct the
traffic to stop and proceed at intersections using red and green traffic light signals as per
the pre-determined time settings.
• The main requirements of traffic signal are to:
(i) Draw attention of the road users
(ii) Enable them to understand the meaning of the light signal
(iii) Provide sufficient time to respond and
(iv) Ensure minimum waste of time.

26. ADVANTAGES OF TRAFFIC SIGNALS
( Properly designed traffic signals at intersections )
• Provide orderly movement of traffic at the intersection.
• The quality of traffic flow is improved by forming compact platoons of vehicles, provided
all the vehicles move at approximately the same speed.
• Reduction in accidents due to crossing conflict, notably the right angled collisions.
• Traffic handling capacity is highest among the different types of intersections at-grade.
• Provide a chance to traffic of minor road to cross the continuous traffic flow of the main
road at reasonable intervals of time.
• Pedestrians can cross the roads safely at the signalized intersection.
• When the signal system is properly co-ordinate, there is a reasonable speed along the
major road traffic.
• Automatic traffic signal may work out to be more economical when compared to manual
control.
DISADVANTAGES OF TRAFFIC SIGNALS
• The rear-end collisions may increase.
• Improper design and location of signals may lead to violations of the control system.
• Failure of the signal due to electric power failure or any other defect may cause
confusion to the road users.
• The variation in vehicle arrivals on the approach roads may cause increase in waiting
time on one of the roads and unused green signal time on other road, when fixed time
traffic signals are used.
• Excessive delay of vehicle may be caused particularly during off-peak hours.
• Drivers may be induced to use less adequate and less safe routes to avoid delays at
signals.

27. DEFINITION OF TERMS USED IN TRAFFIC SIGNAL DESIGN
 The period of time required for one complete sequence of signal indications is called
‘signal cycle’.
 The part of the signal cycle time that is allocated to stop the traffic or to allow traffic
movement is called ‘signal phase’
 The duration of ‘stop’ phase is the red phase and
 The duration of ‘go’ phase is the green phase.
 Any of the division of the signal cycle during which signal indications do not change
is called the ‘interval’.
 The engineer has to design the signal with the sequence and duration of individual
phases to serve all approaching traffic at a desired ‘level of service’.
 The level of service is measured by the vehicle delay, the queue length or the number
of vehicle backed up and the probability of a vehicle entering the intersection during
the first green phase after arrival.
 The capacity of a signalized intersection depends on physical factors of the roads
such as roadway width, number of lanes, geometric design features of intersection
and also the green and red phases of the traffic signal.
 The capacity is also affected by operational and control factors such as number of
turning movement, number and size of commercial vehicles, pedestrian traffic signal
characteristics and abutting land use.

28. TYPES OF TRAFFIC SIGNALS
The signals are classified into the following types:
Traffic control signals
Pedestrian signal
Special traffic signal
THE TRAFFIC CONTROL SIGNAL
 The traffic control signals have three coloured lights which glow facing each direction
of traffic flow namely, red, amber and green.
 The red light is meant for ‘stop’,
 The green light for ‘go’ and
 The amber or yellow light allows the ‘clearance time’ for the vehicles which enter the
intersection area by the end of green time to clear off the intersection, before the
change-over to red signal light.
 A typical traffic signal head is shown in Fig. 5.27.
 Additional signals showing green lights for separate movements of turning traffic
movements may also be provided, where necessary.

30. PEDESTRIAN SIGNALS
 Pedestrian signals may be installed at the intersections controlled by traffic signals
to enable the pedestrians to safely cross the specified roads;
 In such cases, the pedestrian signals and their timings are interlinked to operate
along with the traffic control signal.
 At certain locations of mid-block stretches of urban roads with high demand for
pedestrian crossing, separate pedestrian signals may be installed along with
appropriate warning and informatory signs.
SPECIAL TRAFFIC SIGNALS
 Special traffic signals such as ‘flashing beacons’ may be installed at certain locations
in order to warn the traffic of certain situations.
 At flashing red signals, the drivers of vehicles shall stop before entering the nearest
cross walk at an intersection or at a stop line.
 Flashing yellow signals are cautionary signals meant to signify that drivers may
proceed with caution.

31. TRAFFIC CONTROL SIGNALS
Different types of traffic signals are in use in India namely,
(i) Manually operated signals
(ii) Fixed time automatic signals and
(iii) Automatic traffic-actuated signals.
I) MANUALLY OPERATED SIGNALS
 Each of manually signals is operated from a salient point at or near the intersection
by a traffic police constable;
 The signal phases may be varied depending on the traffic demand at that point of
time.
(II) FIXED TIME AUTOMATIC SIGNALS
 The fixed time automatic traffic signal keeps repeating the same set of signal phases
and the signal cycle time that has been set in the signal controller.
 This type of traffic signal may function satisfactorily at locations where there is no
significant variation in traffic flow on different approach roads.
 U.S.A. fixed time signals are far more numerous than vehicle-actuated types.
 The timing of each phase of the cycle is predetermined based on the traffic studies and
 they are the simplest and cheapest type of automatic traffic signals which are
electrically operated.
 The main drawback is that when the traffic flow on one road may be almost nil and
traffic on the cross road may be quite heavy, yet the traffic in the heavy stream will
have to keep waiting at red phase.

32. (III) AUTOMATIC TRAFFIC- ACTUATED SIGNALS.
 Traffic actuated signals are those in which the timings of the phase and cycle are
changed according to traffic demand.
 Vehicle actuated signals, in which the green periods vary and are related to the actual
demands made by traffic.
 This is made possible by installing detectors on all the traffic.
 Vehicle-actuated signals are very popular in U.K.
(a) SEMI-ACTUATED TRAFFIC SIGNALS
 In semi-actuated traffic signals the normal green phase of an approach may be
extended up to a certain period of time for allowing a few more vehicles approaching
closely, to clear off the intersection with the help of detectors installed at the
approaches.
 Semi-vehicle-actuated signals, in which the right of way normally rests with the main
road and detectors are located only on the side roads.
(b) FULLY ACTUATED TRAFFIC SIGNAL
 In fully actuated traffic movements on the basis of demand and pre-determined
programming.
 But these are very costly to be installed at all intersections.
(c) MODERN FIXED TIME EQUIPMENTS
 Modern fixed time equipments are built for operation with different settings at
certain periods of the day, to cover different conditions.
 This is achieved by providing time switches

33. TYPE ADVANTAGES DISADVANTAGES
Fixed time (i) Simple in construction. (i) Inflexible and hence may
cause avoidable delay.
(ii) Relatively inexpensive (ii) Require careful setting
(iii) Most successfully used in
linked systems requiring a fixed
cycle length for a given pattern
and speed of progression
Vehicle-actuated. (i) They are flexible and are able
to adjust to changing traffic
conditions automatically
(i) Require costly equipment
such as detectors and
sophisticated controllers
Semi-vehicle-
actuated
(ii) Delay is held to minimum and
maximum capacity is achieved.
Useful for junction of a side
street having low traffic volume
with a main street having heavy
flow
(ii) Cannot provide signal
co-ordination.
They are believed to cause
high accident rates at times
of light traffic.

34. CO-ORDINATED CONTROL OF SIGNALS
Co-ordinated signal system
 Co-ordinated signal system on a road net-work of an area is a very complex problem.
 Area traffic control system with co-ordinated signal network is to be implemented
with the help of advanced technology.
Need for co-ordinated control
 Need for co-ordinated control of signals arises on a main traffic route when it is
desirable to reduce delays and avoid main traffic from having to stop at every
junction.
 When a signal indicates a stop aspect at a junction, a queue of vehicles is formed
behind the stop line.
 When the signal changes to green, the vehicles start moving in a platoon.
 If this platoon is made to meet a green aspect at the next junction no delay is caused
to the vehicles.
 This principle of linking adjacent signals so as to secure maximum benefits to the
flow of traffic is called co-ordinated control of signals.
 The co-ordination of signals is bought for with the following objectives in view:
(i) To pass the maximum amount of traffic without enforced halts.
(ii) To have minimum overall delay to traffic streams, both in the main and side roads.
(iii) To prevent the queue of vehicles at one intersection from extending and reaching the
next intersection.

35. TYPES OF CO-ORDINATED SIGNAL SYSTEM
The four basic types of co-ordinated signal systems are:
(i) Simultaneous system, also known as synchronized system
(ii) Alternate system, or limited progressive system
(iii) Simple progressive system
(iv) Flexible progressive system
SIMULTANEOUS SYSTEM
 Under this system, all the signals along a given street always display the same
indication to the same traffic stream at the same time.
 The division of the cycle time is the same at all intersections.
 A master controller is employed to keep the series of signals in step.
The disadvantages of a simultaneous system are:
(i) It is not conductive to give continuous movement of all vehicles.
(ii) The overall speed is often reduced.
(iii) Because the division of the cycle time is the same at all the intersections, inefficiency
is inevitable at some intersection.
(v) The simultaneous stoppage of a continuous line of traffic at all intersections often
results in difficulty for the side street vehicles in turning into or crossing the main
side street.

36. ALTERNATE SYSTEM (LIMITED PROGRESSIVE SYSTEM)
 Under this system, consecutive signal installations along a given road show contrary
indications at the same time.
 This permits the vehicles to travels one block in half the cycle time.
 This system operates efficiency where the blocks are of equal lengths.
 It also brings about a certain measure of speed control since speeding drivers are
stopped at each signal.
Some of the disadvantages of this system are:
(i) The green times for both the main and side streets have to be substantially equal,
resulting inefficiency at most of the intersections.
(ii) In situations where the block lengths are unequal, the system is not well suited.
(iii) Adjustments are difficult for changing traffic conditions.

37. SIMPLE PROGRESSIVE SYSTEM
 In ‘simple progressive system’ a time schedule is made to permit, as nearly as
possible, a continuous operation of groups of vehicles along the main road at a
reasonable pre-decided speed.
 The signals controlling green phases of the traffic signals along this road are
scheduled to work at the predetermined time schedule.
 Though each signal unit may work as fixed time signals, they have equal signal cycle
length and are interlinked so as to operate with the required time off-sets.
 The principle of this simple progressive system is that if a group of vehicles get
released during the green phase at a signalized intersection of the main road, by the
time the first vehicle of this vehicle group travelling at the recommended speed
reaches the next junction, the green phase of this signal would just get started to
allow non-stop movement to the next intersection.
 The non-stop movement for a platoon of vehicles may thus be arranged for the
desired number of intersections on the selected road stretch.
Draw back
 However on urban roads the traffic volume at each intersection may very
considerably; the number of intersecting roads may also very at different junctions.
 Therefore practically it may not be always possible to provide equal signal cycles at
all the intersections along the selected stretch of the main road and so the simple
progressive system may not function effectively.

38. FLEXIBLE PROGRESSIVE SYSTEM
 It is possible to automatically vary the length of signal cycle and signal phase at each
signalized intersection with the help of sensors to detect vehicle arrival and connecting to
a master computer.
 This is the most efficient system of all the four types of traffic signal system.
 This system can function satisfactorily on selected stretches of urban roads with divided
carriageway or on roads with one-way traffic.
 This system is an improvement over the simple progressive system with the following
provisions.
(i) It is possible to vary the cycle time and division at each signal depending upon traffic.
(ii) It is possible to vary the offset, thus enabling two or more completely different plans.
(iii) It is possible to introduce flashing or shut down during off-peak hours.
SIGNAL DESIGN METHODS
 The first two methods are ‘approximate design procedures’.
 Webster’s method of signal design is a rational approach with the objective to minimize the
overall delay of all the vehicles entering the intersection.
 In addition the signal design method as per the guidelines of the IRC is also given.
 For the purpose of simplicity, two phase traffic signals with no turning movements are
illustrated here;
 The methods may be suitably extended for multiphase operations also.
– Trial cycle method
– Approximate method based on pedestrian crossing requirement
– Webster’s method
– Design as per IRC Guidelines

39. TRIAL CYCLE METHOD
 The 15 minute-traffic counts and on road 1 and 2 are noted during the design peak
hour flow.
 Some suitable trial cycle sec is assumed and the number of the assumed cycles in the
15 minutes or 15 x 60 seconds period is found to be (15 x 60)/ i.e.(900/ )
 Assuming an average time headway of 2.5 sec, the green periods and of roads 1 and 2
are calculated to clear the traffic during the trial cycle.
 The amber periods and are either calculated or assumed suitably (3 to 4 seconds)
and the trial cycle length; is calculated, sec.
 If the calculated cycle length works out to be approximately equal to the assumed
cycle length the cycle length is accepted as the design cycle.
 Otherwise the trials are repeated till the trial cycle length works out approximately equal to
the calculated value.
 The design procedure is further explained in Example - 1, given below.
Example - 1
The 15-minute traffic counts on cross roads 1 and 2 during peak hour are observed as 178
and 142 vehicles per lane respectively approaching the intersection in the direction of
heavier traffic flow.
If the amber times required are 3 and 2 seconds respectively for the two loads based on
approach speeds, design the signal timings by trial cycle method.
Assume average time headway as 2.5 seconds during green phase.

40. Solution
Trail (i)
Given 15 min traffic counts sec
Assume a trial cycle sec
Number of cycles in 15 min
Green time for road 1, allowing average time headway of 2.5 sec per vehicle, sec
Green time for road 2, allowing average time headway of 2.5 sec per vehicle sec
Amber time and are 3 and 2 sec. (given)
Total cycle length, C = = 49.4 sec
As this is lower than the assumed trial cycle of 50 sec another lower cycle length may be tried.
Trail (ii)
Assume a trial cycle C(2) = 40 sec
Number of cycles in 15 min 90/40 = 22.5
Green time for road 1, sec
Green time for road 2, sec
Total cycle length sec
Trail (iii)
Assume a trial cycle C(3) = 45 sec
Number of cycles in 15 min = 990/45 = 20
Green time for road 1, sec
Green time for road 2, sec
Total cycle length sec
,,

41. There for the trial cycle of 45 sec may be adopted with the following signal phases:
say adopt sec
say adopt sec
adopt sec, and
Cycle length, C =
A typical layout of traffic control signals with pedestrian signals at the intersection of cross
roads and the traffic signal phase settings for a signal cycle time of 45 sec is shown in fig.
5.28.

42. WEBSTER’S METHOD OF TRAFFIC SIGNAL DESIGN
 It has been found from studies that the average delay and the overall delay to the vehicles at a
signalized intersection very with the signal cycle length.
 The average delay per vehicle is high when the cycle length is very less, as a sizable proportion
of vehicles may not get cleared during the first cycle and may spill over to subsequent cycles.
 As the signal cycle time is increased, the average delay per vehicle decreases up to a certain
minimum value and thereafter the delay starts increasing, indicating that there is an ‘optimum
signal cycle time’ corresponding to least overall delay.
 The optimum cycle time depends on the geometric details of the intersection and the volume of
traffic approaching the intersection from all the approach roads during the design hour.
 Webster’s method of traffic signal design is an analytical approach of determining the optimum
signal cycle time, corresponding to minimum total delay to all the vehicles at the approach
roads of the intersection.
 The field work consists of determining the following two sets of values on each approach road
near the intersection:
(i) the normal flow, q on each approach during the design hour and
(ii) the ‘saturation flow’, S per unit time
 The normal flow values, and on roads 1 and 2 are determined from field studies conducted
during the design hour or the traffic during peak 15 – minutes period.
 The saturation flow of vehicles is determined from careful field studies by noting the number of
vehicles in the stream of compact flow during the green phases and the corresponding time
intervals precisely.
 In the absence of data the approximate value of saturation flow is estimated assuming 160
PCU per 0.3 meter width of the approach road.

43.  Based on the selected values of normal flow, the ratio and are determined on the
approach roads 1 and 2.
 In the case of mixed traffic, it is necessary to covert the different vehicle classes in terms
of suitable PCU values at signalized intersection;
 in case these are not available they may be determined separately.
 The normal flow of traffic on the approach roads may also be determined by conducting
field studies during off – peak hours to be design different sets of signal timings during
other periods of the day also, as required so as to provide different signal settings.
The optimum signal cycle is given by relation
Where
L = total lost time per cycle, sec = 2n + R
n = is the number of phases
R = all – red time or red-amber time; (all-red time may also be provided for pedestrian
crossing)
Y =
Here,
and
Then,
Similar procedure is followed when there are more number of signal phases.
Design of traffic signal timings by Webster’s method is illustrated in Example 5.16

44. Example - 2
The average normal flow of traffic on cross roads A and B during design period are 400
and 250 PCU per hour; the saturation flow values on these roads are estimated as 1250
and 1000 PCU per hour respectively. The all-red time required for pedestrian crossing is
12 sec. Design two phase traffic signal with pedestrian crossing by Webster’s method.
Solution
Given: normal flow on roads A & B: PCU/hr and PCU/hr
Saturation flow, and PCU/hr; all – red time, R=12 sec
number of phase, n = 2
Total lost time, sec
Optimum cycle time, say, 67.5 sec
Provide an all-red time, R for pedestrian crossing = 12 sec
Providing Amber times of 2.0 sec each for clearance, total cycle time
= 29 + 22.5 + 12 + 2 + 2 = 67.5 sec.
Note:
A sketch of a phase diagram as shown in Fig. 5.28 or Fir. 5.30 with the Signal phase and
cycle timings obtained in the above example may be drawn, if needed.

45. DESIGN METHOD AS PER IRC GUIDELINES
• The pedestrian green time required for the major roads are calculated based on walking
speed of 1.2 m/sec and initial walk time of 7.0 sec.
- These are the minimum green time required for the vehicular traffic on the minor and major
roads respectively.
• The green time required for the vehicular traffic on the major road is increased in proportion to
the traffic on the two approach roads.
• The cycle time is calculated after allowing amber time of 2.0 sec each.
• The minimum green time required for clearing vehicles arriving during a cycle is determined for
each lane of the approach road assuming that the first vehicle will take 6.0 sec and
-the subsequent vehicles or the PCU of the queue will be cleared at a rate of 2.0 sec.
- The minimum green time required for the vehicular traffic on any of the approaches is limited
to 16 sec.
• The optimum signal cycle time is calculated using Webster’s formula (explained in method,
given above).
- The saturation flow values may be assumed as 1850, 1890, 1950, 2250, 2550 and 2990
PCU per hour for the approach roadway widths (kerb to median or centre line) of 3.0, 4.0,
4.5, 5.0 and 5.5 m.
- For widths above 5.5 m, the saturation flow may be assumed as 525 PCU per hour per
meter width.
-The lost time is calculated from the amber time, inter-green time and the initial delay of 4.0
sec for the first vehicle, on each leg.
• The signal cycle time and the phases may be revised keeping in view the green time required for
clearing the vehicles and the optimum cycle length determined it steps (d) and (e) above.
• The design method is illustrated in Example - 3

46. Example - 3
At a right angled intersection of two roads, Road 1 has four lanes with a total width of 12.0
m and Road 2 has two lanes with a total width of 6.6m. The volume of traffic approaching
the intersection during design hour are 900 and 743 PCU/hour on the two approaches of
Road-1 and 278 and 180 PCU/hour on the two approaches of Road-2. Design the signal
timings as per IRC guidelines.
Solution
Given: Width of road – 1 = 12.0 m or total 4 lanes, with 2 lanes in each direction;
Width of road - 2 = 6.6 m or total 2 lanes, with one lane in each direction.
Approach volumes on road – 1 = 900 & 743 PCU/hr
On road - 2 = 278 & 180 PCU/hr
Pedestrian walking speed = 1.2 m/sec.
Design traffic on road - 1= higher of the two approach volume per lane
= 900/2 = 450 PCU/hr
Design traffic on road – 2 = 278 PCU/hr
Step – 1. Pedestrian crossing time
Pedestrian green time for road – 1 = sec
Pedestrian green time for road – 2 = sec
Step – 2, Minimum green time for traffic
Minimum green time for vehicles on Road – 1, G (1) = 17 sec
Minimum green time for Road – 1, sec
=

47. Step – 3, revised green time for traffic signals
Adding 2.0 sec each towards clearance amber and 2.0 sec inter-green period for each
phase, total cycle time required = (2 + 17 + 2) + (2 + 27.5 + 2) = 52.5 sec.
Signal cycle time may be conveniently set in multiples of five sec and so the cycle time =
55 sec.
The extra time of 55.0 – 52.5 = 2.5 sec per cycle may be apportioned to the green times of
Road – 1 and Road – 2, as 1.5 and 1.0 sec respectively.
Therefore adopt sec and sec
Step – 4, check for clearing the vehicles arrived during the green phase
Vehicle arrivals per lane per cycle on Road – 1 = 450/55=8.2 PCU/cycle
Minimum green time required per cycle to clear vehicles on Road – 1 = 6 + (8.2 – 1.0)2 =
20.4 sec (less than 29.0 sec and therefore accepted)
Vehicle arrivals per lane per cycle on Road – 2 = 278/55 = 5.1 PCU/cycle
Minimum green time for clearing vehicles on Road – 2 = 6 + (5.1 - 1.0) 2
= 14.2 sec(less than 18.0 sec)
As the green time already provided for the two roads by pedestrian crossing criteria in
Step (2) above are higher than these values (29.0 and 18.0 sec), the above design values
are alright.

48. Step – 5, check for optimum signal cycle by Webster’s equation
Lost time per cycle = (amber time + inter – green time + time lost for initial delay of first
vehicle) for two phases = (2 + 2 + 4) x 2 = 16 sec.
Saturation flow for Road – 1 of width 6 m = 525 x 6 = 3150 PCU/hr
Saturation flow for Road – 2 of width 3.3 m =1850 PCU for 3.0 m wide road + ( 40 * 3/5)
= 1874 PCU/hr
Y = 0.286 + 0.148 = 0.434
Optimum signal cycle time, sec
Therefore the cycle time of 55 sec designed earlier is acceptable.
The details of the signal timings are given below.
These may also be shown in the form of phase diagram as in Fig. 5.30.
Road
Green phase,
G sec
Amber
time, sec
Red phase,
R sec
Cycle time,
C sec
Road 1 29 2 (22 + 2) 55
Road 2 18 2 (33 + 2) 55

49. APPROXIMATE METHOD BASED ON PEDESTRIAN CROSSING REQUIREMENT
The following design procedure is suggested for the approximate design of a two phase
traffic signal unit at cross roads, along with pedestrian signals:
• Based on pedestrian walking speed of 1.2 m per second and the roadway width of each
approach road, the minimum time for the pedestrian to cross each road is also calculated
• Total pedestrian crossing time is taken as minimum pedestrian crossing time plus
initial interval for pedestrians to start crossing, which should not be less than 7 sec
and during this period when the pedestrian will be crossing the road, the traffic signal shall
indicate red or ‘stop’.
• The red signal time is also equal to the minimum green time plus amber time for the traffic
of the cross road.
• The actual green time needed for the road with higher traffic is then increased in
proportion to the ratio of approach volumes of the two roads in vehicles per hour per lane.
• Based on approach speeds of the vehicles, the suitable clearance interval between green
and red period i.e., clearance amber periods are selected.
• The amber periods may be taken as 2, 3 or 4 seconds for low, medium and fast
approach speeds
• The cycle length so obtained is adjusted for the next higher 5 – sec interval; the extra time
is then distributed to green timings in proportion to the traffic volumes
• The timings so obtained are installed in the controller and the operations are then observed
at the site during peak traffic hours; modification in signal timings are carried out if
needed
• The design of a simple two-phase signal is illustrated by Example - 2 given below.

50. Example - 4
An isolated traffic signal with pedestrian indication is to be installed on a right angled
intersection with road A, 18 m wide and road B, 12 m wide. During the peak our, traffic
volume per hour per lane of road A and road B are 275 and 225 respectively. The
approach speeds are 55 and 40 kmph, on roads A and road B respectively. Assume
pedestrian crossing speed as 1.2 m per sec. Design the timings two-phase traffic and
pedestrian by the approximate method.
Solution
Given: Widths of road A = 18 m and of road B = 12 m
Traffic volumes on road A = 275 and on road B = 225 vehicles/lane/hour
Approach speeds on road A = 55 and on road B = 40 kmph
Pedestrian crossing speed = 1.2 m/sec
Design of two-phase traffic control signals
Pedestrian crossing/clearance time for Road A = 18/1.2 =15 sec
Pedestrian crossing/clearance time for Road B = 12/1.2 = 10 sec
Adding 7 sec initial walk period,
minimum red time for traffic of road A, is (15 + 7) = 22 sec and
that for road B is (10 + 7) = 17 sec.
Minimum green time, for traffic of road B,
based on pedestrian crossing requirement = 22-3 = 19 sec.
Minimum green time, for traffic of road A,
based on pedestrian crossing requirement = 17- 4= 13 sec.

51.  The minimum green time calculated for road A is with respect to pedestrian crossing time
required for the narrower road B.
 As road A has higher traffic volume per lane than road B, the green time of road A has to
be higher than that of road B;
 the increase may be proportion to the approach volume of road A with respect to that of
road B.
Let and be the green times and be the approach volume per lane
Using the relation,
Green time for traffic is taken as the minimum value = 19 sec as obtained from pedestrian
crossing criterion for the wider road A.
Green time for traffic of road A may be increased in proportion to higher traffic volume
Using relation sec
Based on the approach speed of 55 kmph for road A, amber period, sec
For road B with 40 kmph, amber period, sec
Total cycle length
Therefore adopt signal cycle length of 50 sec.
The additional period of 50 – 49.2 = 0.8 sec is distributed to green timings in proportion to the
approach traffic volume. Therefore the revised signal phase are:
sec, adopt 23.5 sec sec, adopt 19.5 sec
Therefore cycle time, C = 23.5 + 19.5 + 4 + 3 = 50 sec

52. Design of pedestrian signals:
Do not Walk (DW) period of pedestrian signal at road A ( is red period of traffic signal at
B.
For , sec
For , sec
Pedestrian clearance intervals (CI) are of 15 and 10 sec respectively, for roads A and B for
crossing. The walk time (W) is calculated from total cycle length.
For , sec
For , sec
A typical layout of traffic control signals with pedestrian signals at the intersection of cross
roads is shown in Fig. 5.29.
A phase diagram may be drawn incorporating the above values of traffic and signal time
settings, as shown in the Fig. 5.30.

54. TRAFFIC ISLANDS
DIFFERENT TYPES OF TRAFFIC ISLANDS
 Traffic islands are raised areas constructed within the roadway to establish physical
channels through which the vehicular traffic may be guided.
 Traffic islands often serve more than one function.
 Based on the function, traffic islands may be classified as:
– Divisional islands
– Channelizing islands
– Pedestrian loading islands
– Rotary
ROTARY ISLAND
• Rotary island is the large central island of a rotary intersection;
• This island is much larger than the central island of channelized intersection.
(see Fig. 5.35 and 5.36).
• The crossing manoeuvre is converted to ‘weaving’ by providing sufficient weaving
length.

57. ROATARY INTERSECTION
FUNCTIONING OF A ROTARY INTERSECTION
 A rotary intersection or traffic rotary is an enlarged road intersection where all
converging vehicles are forced to move round a large central-island in one direction
before they can weave out of traffic flow into their respective directions radiating
from the central island.
 In India and other countries which follow ‘keep to the left’ regulation, clock-wise
direction of flow around the island is followed.
 The main objects of providing a rotary are to eliminate the necessity of stopping even
for crossing streams of vehicles and to reduce the area of conflict.
 The crossing of vehicles is avoided by allowing all vehicles to merge into the streams
around the rotary and then to diverge out to the desired radiating road.
 Thus the crossing conflict is eliminated and converted into ‘weaving manoeuvre’
which consists of
(i) Merging manoeuvre from the left and diverging out to the right
or
(ii) A merging form the right and a diverging out to the left.
A typical rotary intersection and the functioning is shown in Fig. 5.35.

58. DESIGN FACTORS OF A ROTARY.
(1) Design speed: Vehicles approaching intersection have to reduced speed, than the design
speed of road.
(2) Shape of Central island:
- It depends on number and layout of intersecting roads.
- The various shapes considered are circular, elliptical, turbine and tangent shapes.
(3) Radius of rotary roadway:
- Rotary around the central island has different radii at different points depending on shapes
of central island.
- Recommended minimum radii of central island is 1.33 times the radius of entry curve.
- Radius at entry is 25 – 35 m.
(4) Width of the rotary roadway:
-The minimum width of carriage way at entrance and exit should be 5 m and
- All the traffic rotary have to go round the one-way rotary roadway at-least a short distance.
- The minimum width of rotary roadway between the edge of central island and adjoining
kerb is effective width of rotary.
(5) Weaving angle and weaving distance:
-The Angle between path of vehicle entering the rotary and that of another vehicle leaving the
rotary is called weaving angle.
- The length between 2 channelizing islands of adjacent roads where weaving operation takes
place is called weaving length.
- Recommended value of this 45-90 m for 40 kmph design speed.

59. ADVANTAGES OF ROTARY
(i) Crossing manoeuvre is converted into weaving or merging and diverging
operations.
- Hence there is no necessity of any of the vehicles, even those which have to go in
cross directions to stop and proceed within a traffic rotary.
- Thus the journey is more consistent and comfortable when compared with any
other intersection at grade.
(ii) All traffic including those turning right or going straight across the rotary have
equal opportunity as those turning left.
(iii) The variable vehicle operation cost of motor vehicles is lower at a traffic rotary than
at a signalized intersection where the vehicles have to stop and proceed.
-Though the distance to be traversed by vehicles which are to turn to the right or proceed
straight across is higher, still the fuel consumed in the process of crossing the rotary
intersection is likely to be lower.
- This is because one stop-proceed operation at a signal is likely to consume fuel
required for travelling about 275 m at uniform speed without stopping.
(iv) There is no necessity of traffic police or signal to control the traffic as the traffic
rotary could function by itself as a traffic controlled intersection and
- is the simplest of all controls.
- The maintenance cost is hence almost nil.

60. (v) The possible number of accidents and the severity of accidents are quite low because
of low relative speed.
-Further weaving, merging and diverging manoeuvres are easier and less dangerous
operations than crossing.
- Check on speed of vehicles is automatically enforced by proper design.
(vi) Traffic rotaries can be constructed with advantage when the number of intersecting
roads is between four and seven.
(vii) A rotary is more advantageous than a signalized intersection, when the proportion
of right turning traffic exceeds 30 percent at a four legged intersection.
(viii) The capacity of rotary intersection is higher than un-channelized and channelized
intersections.
- The rotary intersection can efficiently handle up to about 3000 vehicles per hour
entering from all intersecting legs.
- The capacity of the rotary intersection can be increased up to 5000 vehicles per
hour, by appropriate design.

61. LIMITATIONS OF ROTARY
(i) Rotary requires comparatively a large area of land and so where space is limited and
costly as in built up areas, the total cost may be very high.
(ii) Where pedestrian traffic is large as in urban areas, the rotary by itself cannot
control the traffic and hence will need grade separated pedestrian crossing;
- alternatively pedestrians crossing has to be supplemented by traffic police.
- If the vehicular traffic has to stop to allow pedestrian to cross, the main purpose of
rotary is defeated.
(iii) Design of rotary become too elaborate and operation and control of traffic also
become complex, in places where there is mixed traffic and large number of cyclists
and pedestrians.
(iv) Rotaries are unsuitable, where the angle of intersection of two roads is too acute or
when there are more than seven intersecting roads.
(v) Rotaries become troublesome, when the distance between intersections on an
important highway is less,
(vi) Where there are a large number of cycle and animal drawn vehicles, the extra length
to be traversed by crossing and right turn traffic is considered troublesome and there
is a tendency to violate the traffic regulation of clock wise movement around the
central island.

62. ROAD MARKINGS
OBJECTS
 Road or traffic markings are made of lines, patterns, words, symbols or reflectors
on the pavements, kerb, sides of islands or on the flexed objects within or near the
roadway.
 Traffic markings are intended to regulate, control, warn or guide the traffic/road
users.
 The markings are made using specified type of paints in contrast with colour and
brightness of the pavement or other back ground or by road studs.
ROAD MARKING MATERIALS
• ‘Thermo-plastic paint applied hot’ fulfilling Clause 803 of MORTH Specification
should be preferred wherever feasible, as they have better visibility and longer
service life when compared with light reflecting road marking paints.
• Night visibility under normal head light of vehicles is improved by embedding glass
beads in the pavement marking material.
• Pre-fabricated sheet material may also be used for road marking.
 Other materials used are pre-fabricated plastic tape, reflectorised stripping powder
and road studs made of solid white heads or reflex lens.

63. CLASSIFICATION OF MARKING
• CARRIAGEWAY MARKINGS – longitudinal markings such as centre line, traffic
lanes, border or edge lines, bus lane, etc. and ‘no parking zones’, ‘warning lines’,
etc.
• MARKINGS AT INTERSECTIONS – stop lines, pedestrian crossings, direction
arrows, give way, marking on approaches to intersections, speed change lanes, box
marking, etc.
• MARKING AT HAZARDOUS LOCATIONS – obstruction approaches,
carriageway width transition, road-rail level crossings, check barriers, etc.
• MARKINGS FOR PARKING – parking space limits, parking restrictions, bus stops,
etc.
• WORD MESSAGES – stop, slow, bus, keep clear, right turn only, exit only, etc.
• OBJECT MARKING – kerb marking, objects within the carriage way, objects
adjacent to the carriageway, etc.

64. ROAD DELINEATORS
 Road delineators are devices or treatment to outline the roadway or a portion there
of to provide visual assistance to drivers about the alignment of a road ahead
especially at night.
 Three types of delineators that may be used are
-‘ROADWAY INDICATORS’
-‘HAZARD MARKERS’
- OBJECT MARKERS’.
ROADWAY INDICATORS
 Road way indicators are in the form of guide posts, 0.8 to 1.0 m high and painted by
black and white strips with or without reflectors and are intended to delineate the edges of
the roadway so as to guide the drivers about the alignment ahead.
HAZARD MARKERS
 Hazard markers are approximately 1.2 m high plates on posts, either with three red
reflectors or markers with black and yellow strips at 45° towards the side of obstruction,
meant to define obstructions or objects close to road:
OBJECT MARKERS
 Object markers are circular red reflectors arranged on triangular or rectangular panels
and are used to indicate hazard and obstructions within the path of vehicles, like the
channelizing island placed close to the intersections.

65. HIGHWAY LIGHTING
Importance of highway lighting
 The rate of highway accidents and fatalities that occur during night driving is several
times higher than that during day driving day driving, when expressed in terms of
vehicle-kilometeres travelled during night and day time.
 One of the various causes of increased accident rate during night may be attributed
to poor night visibility.
 Highway lighting is particularly more important at intersections, bridge site, level
crossings and in places where there are obstructions to traffic movements.
 Lighting on rural roads has not yet become common, evidently due to the cost
consideration and less number of pedestrians and other slow traffic using the facility
at night.
 On urban roads where the density of population is also high, road lighting improves
the visibility and safety;
 other advantages of road lighting is the general feeling of security and protection and
reduction in crimes.
 Thus even though head lights of vehicles may be sufficient for safe night driving, still
road lighting may be considered as an added facility to the road users.

66. PRINCIPLE OF VISIBILITY AT NIGHT
 During night driving the manner in which objects are visible varies brightness of the
road surface and the object.
SILHOUETTE -When the brightness of the object is less than that of the background,
that is when the object appears darker than the road surface.
 If the brightness of the pavement is uniformly increased, Hence it is obvious that
night visibility on cement concrete and other light coloured pavements are better
than on black-top surfaces.
 A light coloured, rough textured pavement surface that can reflect light back is
considered most desirable.
 Surface that becomes mirror like or shiny when wet (such as smoothened black-top
road surface) should be avoided as pratically no light reflects back from them.
REVERSE SILHOUETTE - When the brightness of an object is more than that of the
immediate background.
 The objects adjacent to the roadway, projections above the pavement surface such as
island or vehicles may be seen by this process of reverse silhouette.
 When the pavement surface is very dark like black-top surface, the object which are
relatively brighter in colour are seen by this process.

67. FACTORS WHICH INFLUENCE NIGHT VISIBILITY
• Amount and distribution of light flux from the lamps
• Size of object
• Brightness of object
• Brightness of the background
• Reflecting characteristics of the pavement surface
• Glare on the eyes of the driver and
• Time available to see an object
DESIGN FACTORS
The factors to be considered in the design of road lighting are;
• Lamps
• Luminaire distribution of light
• Spacing of lighting units
• Height and overhang of mounting
• Lateral placement
• Lighting layouts

68. LAMPS
• It is economical to use the largest lamp size in a luminaire which will provide
sufficient uniformity of pavement brightness; but this also depends on the spacing of
the lamps.
• The various types of lamps in use for highway lighting are filament, fluorescent and
sodium or mercury vapour lamps.
• Filament lamps are not at all preferred these days.
- Because though the initial cost of the filament lamp is lowest of all these, the energy
efficiency is the lowest and
- the luminaire distribution is also not satisfactory
• Sodium-vapour lamps are preferred at large intersections.
LUMINAIRE DISTRIBUTION OF LIGHT
• To have the best utility of the luminaire or source of light, it is necessary to have
- proper distribution of light, - illuminate the pavement and adjacent area (cover the
pavement between the kerbs and provide adequate lighting on adjacent area such as
foot paths or the shoulders, for 3 to 5 m beyond the pavement edge), - produce
maximum uniformity of pavement brightness.
• It is suggested that from BIS , the average level of illumination on road side may be
20 to 30 lux on urban roads carrying fast traffic and
• about 15 lux for other main roads carrying mixed traffic and in arterial roads.
• In secondary roads the level of illumination may be 4 to 8 lux depending on traffic.
• The ratio of minimum to average illumination being 0.4

70. SPACING OF LIGHTING UNITS
• The spacing of lighting units is often influenced by the electrical distribution poles,
property lines, road layout and type of road side features and their illumination.
• Large lamps with high mountings and wide spacing should be preferred from
economy point of view.
HEIGHT AND OVERHANG OF MOUNTING
 The distribution of light, shadow and the glare effect from street lamps depend also
on the mounting height.
 The glare on eyes from the mounted lights increases with the power of the lamp
directed towards the eye and decreases with increase in height of mounting.
 Usual mounting heights range from 6 to 10 m
 The minimum vertical clearance required for electric power lines up to 650 volts has
been specified as 6.0 m above the pavement surface by the Indian Roads Congress.
• Over hangs on the lighting poles would keep the poles away from the pavement.
• This enables better distribution of light on the pavement and less glare on eyes of
road users.
• It is desirable to have higher mounting heights and adequate overhang projections.
• Fig. 5.41 Effect of mounting height and overhang on length of shadow

72. LATERAL PLACEMENT
 The Indian Roads Congress has specified the horizontal clearance required for lighting
poles as given below:
• For roads with raised kerbs, (as in urban roads): minimum 0.3 m and desirable 0.6 m
form the edge of raised kerb
 For roads without raised kerbs, (as in rural roads): minimum 1.5 m from the edge of the
carriageway, subject to a minimum of 5.0 m from the centre line of the carriageway
• The clearance specified above apply to the poles carrying electric power and also
telecommunication lines.
LIGHTING LAYOUTS
On straight roads the lighting layout may be of the following types:
(1) Single side, (2) Staggered, on both sides, (3) Central
 Single side lighting is economical to install; but it is suitable only for narrow roads.
 Due to cost considerations even on two lane roads often single side lighting is adopted.
 For wider roads with three or more lanes the staggered system or the central lighting
system may be adopted. (These systems of lighting layouts are illustrated in Fig. 5.42.)
 The spacing of the lights in each of these systems is decided based on various
considerations including location, lamp size, height of mounting and lighting
requirements.
 Lights are installed at closer spacing on curves than on straights.
 The lights are located on the outer side of the curves to provide better visibility.
 The layout of lighting on horizontal curves is shown in Fig. 5.43.
 At vertical summit curve lights should be installed at closer intervals near the summit.

75. • At intersections, due to potential conflicts
of vehicular and pedestrian traffic, more
illumination is required.
• For simple intersections in urban area,
the illumination should be at least equal
to the sum of illumination values for two
roads which form the intersection.
• The suggested lighting layouts for typical
intersections are shown in Fig. 5.44.
• A detailed traffic volume and flow study
should be made in the cases of compound
intersections before deciding the layout of
lights.
• The lighting unit should be located near
the pedestrian crossing, channelizing
islands and signs.
• The lighting layout for traffic rotaries
has been shown in Fig. 5.35.
• Bridges: Bridges present special problem
because it may not be possible to have
standard mountings of 9m or so.
• The lantern may have to be mounted on
parapet, height rarely exceeding 3-5m
above the deck
• This necessitates the luminance to be
restricted if glare is be avoided.

77. DESIGN OF HIGHWAY LIGHTING SYSTEM
• For various types of luminaire distribution, the utilization coefficient charts are
available for determination of average intensity of light in lux over the roadway
surface where lamp lumen, mounting height, width of paved area and spacing
between lighting poles are known.
• The typical utilization coefficient chart is shown in Fig. 5.45.
 The following relationship is used for computation of spacing between the lighting
units:
Spacing (Eq.5.35)
 The coefficient of utilization is obtained from the appropriate chart, as in Fig. 5.45.
 The maintenance factor takes into account the decrease in efficiency of lamp with
age and an average value of about 80% may be assumed.

79. Example - 5
A street lighting system is to be designed for the following conditions:
Street width - 15 m
Mounting height - 7.5 m
Lamp size 6000 lumen
Luminaire type - II
Calculate the spacing between lighting units to produce average lighting intensity of 6.0
lux, using the given coefficient of utilization chart. (Refer Fig. 5.45)
Solution
Given: Street width = 15 m,
Mounting height = 7.5 m,
Lamp size = 6000 lumen
The ratio =
From Fig. 5.45, coefficient of utilization for the ratio of road width to height = 0.36
Assume a maintenance factor = 0.8
Spacing =
= (6000 x 0.36 x 0.8) / (6 x 15) = 19.2 m

80. ROAD SIDE ARBORICULTURE OR FURNITURE
 The word arbori is originated from latin word arbor meaning tree
 Arboriculture means tree culture, that is care and planting of trees
 It is important for roadside development
 The distance b/w two trees generally 10 to 20 m. It varies depend on nature of trees
OBJECTIVES OR IMPORTANCE
 To provide an attractive landscape of the road side to road users
 To provide shade to the road users
 To provide good timber and fruits. There by generating a source of revenue of
government
 To prevent movement of sand in desert areas
 To stabilize the formations
 To break the monotony of long road and make the driving enjoyable
 To prevent the bleeding of bituminous road surface.
 To reduce the temperature variations of road surface.

81. Explain design factors of highway lighting. (10M)
Ans: Highway Lighting Design Factors:
(i) On a straight road, the lighting layout may be single sided staggered opposite or central.
Single sided lighting: Used in narrow roads, simple arrangement usually adopted in 2 lane
roads and is cost effective.
Central lighting: Used when sides of roads has trees and unavoidable structures.
Staggered lighting: Used for wider roads with 3 or 4 lanes and also used for curves.
Opposite lighting: Used when width of road is more. It results is a uniform dominance over
the full pavement width.
(ii) At junctions and cross roads: A high standard of lighting is needed at junctions as many
accidents can be prevented with adequate illumination. In case of T junction, it is customary
to locate a lantern in the major roads just beyond the entrance from the side road. In case of
cross roads, the idea is to locate lantern a little beyond the intersection in each road so as to
show-up the curb line as dark shadow to all users of the junction.
(iii) At traffic rotaries: At entry to the rotary the driver should be able to see his path and also
other vehicles. A common practice is to light the central island from lantern supported by
columns erected on the central island if diameter of island is less than 20m.
(iv) On curves: When a staggered arrangement of lanterns is employed in the straight length
of road, uniform, standard or road brightness may be achieved on bends in both cutoff and
semi-cutoff installations by setting lanterns on the outside of bends.
(v) Bridges: Bridges present special problem because it may not be possible to have standard
mountings of 9m or so. The lantern may have to be mounted on parapet, height rarely
exceeding 3-5m above the deck. This necessitates the luminance to be restricted if glare is be
avoided.