Expressway Traffic Managemnt1

8/4/2019 Expressway Traffic Managemnt1

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Chapter 1: Expressway Safety

An accident may be considered as a random multi-factor event involving the road

user, the vehicle and the road environment. The user perceptions are usually

associated with the requirement for speed, comfort, safety and aesthetics. Effective

ways of optimizing road safety in India are i) proper maintenance and ii)

disseminating traffic information along the expressways. This chapter deals with

various locations of safety hazard, safety measures, which should be taken into

account during planning and designing, and operational stage of expressways.

1.1 Safety Hazards for Expressways

The common safety hazards on expressway are Drivers Behaviour, Visibility Road

and Assets, Extreme weather Conditions and Road Geometry. Road user behaviour

and awareness of road safety aspects is an ongoing process in India. Extreme

weather conditions are not in control. The important aspect to improve road safety is

adequate geometric design and improvement of visibility on expressways. The

aspects of uniformity in design, homogeneity in traffic streams and predictability for

road user will enhance road safety in a big way. In order to achieve the road safety

the common areas of safety hazards on expressways are Horizontal Curves, Vertical

Gradients, Intersections, Toll Plazas, Entry Exit Ramps, Animal Crossings and Urban

Areas.

Expressways are designed for high speed long distance travel. The main objective of

developing expressway is segregation of through traffic from local traffic. All local

traffic movement shall be provided on separate service roads and underpasses. The

expressway traffic shall be provided with uninterrupted traffic movement. In order to

achieve this goal of High-speed and safety, the traffic has to enter and exit the

expressway only through interchanges.

Weather conditions like heavy rain, fog, storm, gust, dust storm, hail, etc., imposehazards to expressways. Two major hazards for high speed traffic are hydroplaning


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and poor visibility. Especially water shows different character when it encounters a

high speed contact as featured hydroplaning. Heavy vehicles can cause ruts in the

pavement over time, which allow water to pool. Hydroplaning occurs when a tire

encounters more water than it can dissipate. Hydroplaning can be expected at

speeds above 70 km/h, where water ponds to a depth of at least 2.5 mm over a

roadway length of 9 meters or more. Water staying on the surface of carriageway not

only reduces the skid resistance between tires and pavement surface but also

produces hydroplaning. In rainy days frequent traffic accidents used to be observed

on regular dense asphalt pavement. This proves the importance of water discharge

from the surface of expressways more than ordinary roads.

Places where a road vertical gradient changes into an ascent from a descent, some

drivers may unconsciously lose their speed and the distance between the leading

vehicle and the vehicle behind may be shortened as the result. In these cases, the

following drivers are forced to brake one another, therefore the traffic becomes

congested. When vehicles concentrate on the passing lane to overtake slow-moving

vehicles ahead, the same phenomenon occurs. Some drivers may also slow down

when trying to enter the main traffic flow at a merging point from an interchange.

Traffic congestion also often occurs from a temporarily inadequate road capacity dueto the stopping of vehicles at a tollgate. Adequate information shall be provided to

road user in advance at these locations.

1.2 Safety Measures and Devices for Expressways

Visibility is very important for high-speed driving. Impaired visibility is a great hazard

to expressway safety. Motorways and expressways

are characterized by divided carriageway, access

controlled, grade-separated, entry and exit allowed

only through interchanges, and high speed vehicle

only are allowed to use. These features actually make

them the safest roads among all kinds of roads.

Motorways and expressways shall be equipped with

advanced road safety devices and ITS applications.

Although there are many road safety devices, whichare used for both expressways and ordinary roads,


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there are many special and expensive devices, which are used only for

expressways.

Road Markings

Anti-Glare Devices

Expressway Lighting

Delineators

Safety Barriers

Road Signs

Intelligent Transportation Systems

1.2.1 Road Markings

Road markings can play a key

role in reducing the accident toll

and facilitating traffic flow. It is

difficult to visualize an

expressway without its markings.Road markings have three main

functions: 1) to guide and channel

the traffic, 2) to define the

territorial limits of each road user,

and 3) to warn of approaching

obstacles, hazards like diverging

noses. Applying high visibility

road markings with sound and

vibration function for the edge line

of the carriageway are very

effective not only for enabling

drivers to see the lane markings clearly at night but also for giving drivers a warning

when they inattentively deviate from the carriageway. Especially thermoplastic road

markings and rumble strips are to be provided.


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A section of a sharp curve is always one of the accident-prone points and needs to

be equipped with safety measures. A combination of safety devices, which suite to

the particular section, should be carefully planned. Most economical and effective

safety measures, which should be planned as the first remedy, are to improve

visibility by delineators and chevron panels, and to disseminate warnings to drivers

by cautionary signs. As for chevron panels, it improves the effectiveness by

changing colours. As for the secondary remedy or higher level countermeasures,

porous pavement for rainy day accidents and high-brightness LED delineators for

night accidents should be planned. Merging points is also one of the accident-prone

points.

A car has to accelerate to the speed of the main traffic and merge in the space

between vehicles. The car has to

know the condition of main traffic

before trying to do so. The clearance

zone provides good sight distance

for both the merging vehicles and

main traffic vehicles.

1.2.2 Anti-Glare Devices

Anti-glare devices are installed for

reducing the headlight glare of


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opposing traffic at night, which may distract the driver from driving tasks. This

contributes to reduce the number of traffic accidents. The commonly used materials

are net types and board types. Installation of anti-glare devices depends on many

factors such as accident experience, high night-time traffic volumes, or severe

highway geometry. For sections of crest or curves with the horizontal curvature

radius is smaller than 750 m, it is desirable to install them. Anti-glare devices are

generally installed on the median strips. Desirable spacing is 4 m and the height is

set at 1.4 m considering the height of headlight of passenger cars and large-sized

vehicles running in the opposite directions. Installation of anti-glare devices are not

required at places where continues street-lighting is provided. Installation of anti-

glare devices shall be provided with the following characteristics of expressway:

The median strip has a width of less than 7 m.

The difference in the elevation of opposing directions is less than 2 m.

1.2.3 Expressway Lighting

The main objective of lighting is to illuminate the carriageway, objects within ROW

and environment, especially during foggy and rainy weather as well as at night. The

expressway lighting is warranted to

provide adequate visibility to motorists

during day in inclement weather and

night for defining road geometry, object

and the road environment. Expressway

lighting is of special significance at

potential accident sites, traffic

interchange points such as interchanges,

terminals, toll plazas and wayside amenities.

Recommended guidelines for Expressway lighting in Indian situations as follows:

Where expressway passes through urban or suburban areas for a length of 3

km.


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Where three or more interchanges are located with an average spacing of 3

km or less.

Where an expressway section with AADT of 30,000 or more is located near

cities.

1.2.4 Delineators

Major causes of visibility impairing

weather are fog, rain, snow, and

dust storm. These weathers are,

however, seldom last long hours

and disappear as the time

elapses. However, as the motor

vehicles have come to constitute

very important part of social

activities like today, we simply

cannot accept the problem of

visibility impairing by bad

weathers. Self-luminous

delineators, halogen delineators,

high visibility road markings,

externally illuminated road signs,

self-luminous chevron panels;

these are now commonly used to improve visibility during bad weathers. Therefore,

considering the fog occurrences during winter season, it is desirable to adopt a

measure, which has a small initial cost rather than a high operational cost.

Lateral delineator posts are made of plastic retro-reflectors so as to be highly visible

both by day and by night. Chevron-type panels delineate curves quite clearly. Being

properly placed, they ensure visual guidance to traffic. Road work signing and

delineation regularly use such safety devices as well. Using high performance retro-

reflective materials no longer require frequent maintenance. However, they are often

in places where they are easily knocked down in the event of a vehicle leaving the

curve. Retro-reflective road studs are used in addition to road markings where


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circumstances demand, both as a center line and as edge delineation of

carriageways and roads. Products of solar-powered type are available for all kinds of

curve indicators. When the road condition is especially bad due to a sharp curve or

frequent fog, for example, self-luminous types show high performance during night

and bad weather like rain and fog.

Delineators are erected along the

roadsides and indicate the road

alignment. It functions mainly at night to

guide the drivers. The delineators are

effective in promoting safe driving by

providing advance information of the

alignment, which serves to prevent

traffic accidents. Self-luminous

delineators have been found very

effective to reduce the number of traffic

accidents. The self-luminous

delineators, which consist of an internal

light source and a controller to flash automatically, are to be installed mainly incritical expressway sections. The power source for the self-luminous delineator is

either by electricity line or solar battery.

1.2.5 Safety Barriers

The safety barrier is designed to

absorb the impacts and redirects the

vehicle back into carriageway by

breaking back. Safety barrier is also

designed to cover the edge of

structures like a tunnel, a bridge or a

lighting pole so that a deviated

vehicle from the carriageway would


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not hit it directly. Safety barrier shall be provided adequately at critical locations of

the expressway.

Safety Fence

Hitting of animals on the expressway can result into dangerous situations because

many of the drivers who hit animals try to dodge them and lose control of their

vehicles. Proper animal crossing is useful for safety for both animals and drivers on

expressways. Safety fence along the expressway shall be provided to animals

crossing the expressway. The fencing cordons off not only animals but also people

mistakenly or maliciously trying to enter ROW of the expressway.

Boundary Fence

Boundary fences are installed to prevent unauthorized people or animals from

entering the expressway and to prevent encroachment on right-of way. Boundary

fences should be installed on 1) sections where other roads are adjacent to the

expressway, 2) sections with housed adjacent to the expressway, 3) sections with a

less-than-3-m difference in elevation between the expressway and the outside land,

4) around such facilities as interchanges or service areas, and 5) areas under

viaducts.

Fence Against Falling Objects

The purpose of installation of fences against falling objects is the prevention of

objects from falling over-bridges down to expressways or the prevention of objects

from jumping beyond the vehicles on expressways to areas put of the expressways,

to ensure traffic safety. Fences to prevent falling objects from height should be

installed at over-bridges, flyovers and densely populated areas, sections crossing or

nearing railways. The area of installation of fences to prevent objects falling off

expressways includes the area crossing the facility to be protected and adjacent

allowance area. The adjacent allowance area is represented by a tangent at a 15

degrees.

1.2.6 Toll Plazas


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At toll plazas, advanced guide signs and special marking for ETC make drivers

prepared.

Success of expressway is always linked with successful toll-plaza operations

with efficiency. Segregation of ETC vehicles from others is crucial to have

smooth traffic flow and avoid traffic congestion. Safety of toll booth operators

is very important. The toll-plaza shall be equipped with underground tunnel

for safe movement of toll-booth operators.

1.2.7 Entry Exit Ramps


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All Traffic congestion tends to concentrate at

merging and diverging points. These points

should be properly equipped with safety devices

such as blinkers and cushion drums.

1.3 Road Signs

Road Traffic signs plan very important role in smooth and safe traffic movement.

Adequate information to be given to the road user for smooth and safe movement of

traffic. Alll important traffic diversion locations, Gantry-Signs shall be provided for

traffic guidance. All traffic signs shall be provided with retro-reflective material as per

the standards of IRC.

1.4 Wayside Amenities

Wayside Amenities shall be provided adequately at designated locations with proper

parking facilities. All hotels located along the expressway shall have adequate

parking space, smooth entry and exits. All facilities provided along the expressway

shall be controlled by a traffic personnel.

1.5 Rescue and Relief Operations

The toll plaza shall be equipped with adequate emergency relief equipment such as

cranes and ambulances. In case of an accident, the Golden-Hour concept shall be

followed to save lives. The accident victim shall be taken to nearest hospital within 1


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hour. Provision of Helipads along the critical areas of expressway and Trouma-care

centres shall be provided with Helipads.

1.6 Expressway Patrol

Expressway Patrol is very important maintenance activity. The highway patrol shall

perform the routine checking of expressway assets, crowd control and reporting to

control. The expressway patrol is more needed during peak-hours and night-time.

Chapter 2: Real-Time Traffic Management With

Intelligent Transportation Systems

Road traffic exhibits high rate of traffic congestion or accident, as in comparison to

other transport modes like trains and airplanes. The measures to build new roads to

reduce congestion and accidents are often limited, in terms of time, cost and impact

and most frequently existing measures have only limited effectiveness. The

information technology (ITS) allows vehicle safety measures or traffic controls to be

conducted efficiently and effectively, like other transportation modes. And ITS can be

introduced with lower cost and in a shorter time period than building new roads.

Expressways, which are meant for high-speed traffic, use ITS positively ranging from

electronic toll collection, traffic control and information, and road and facility

management. Various ITS technologies are used to integrate these functions, as the

Intelligent Transport Systems (ITS).

During course maintenance or an incident, traffic diversion measures such as

closure of the shoulders, closure of lane, diversion of all traffic into one carriageway,

temporary reduction of maximum speed limit etc. will be adopted. Drivers should be

given warning of such operation well far enough distance in advance.

Providing information on obstacles ahead, where roadside sensors detect stopped

vehicles or congestion beyond a curve with poor visibility and warn drivers entering

the curve through visual and audio information. Providing information on conditions

ahead, where drivers are provided with visual information on road conditions ahead


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to enable them to choose the best route. Merging assistance, where to prevent

impact accidents at merging points, vehicles approaching a merging point are

detected from the roadside: just before the merging point, drivers on the main lanes

are provided with easy-to-understand information on the presence of merging

vehicles. Provision of VMS at all entry and exit points of expressway is necessary for

safety and information.

2.1 Real-Time Traffic Management System (RTTMS)

The RTTMS shall cover the entire Expressway including ramps leading to and from

the main Expressway road. The RTTMS shall cover all functions which are

necessary for monitoring and management the Expressway operation and detect

incidents and other dangerous traffic situations. The RTTMS shall comprise the

following subsystems:

Traffic video surveillance with CCTV Cameras

Traffic control with VMS

Incident Management with Incident Detection Sensors

Control Room Equipment - CCTV LCD monitors System Hardware and

Software

The operation of the RTTMS shall be based on video (image processing)

technology. Video imagery shall be fed from fixed cameras installed along the entire

Expressway to the central processing system for analysis. Working system of

RTTMS is present in the form of a Block-Diagram.


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2.2 Video Processing

Fixed cameras shall be installed along the entire Expressway, and on all ramps

leading to or from the main road. The fixed cameras shall be installed in lighting

masts (minimum height: 7 m above carriageway), placed on/between the roads

centre dividers. The camera housing shall have appropriate shielding mechanism to

prevent unwanted sunlight and reflections of sunlight to appear on the imagery. The

video processing shall accomplish two different tasks:

Detection of traffic incidents

Monitoring of traffic speed and volume

Traffic data shall be transmitted to the control room in real-time for display and

storage.


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2.3 VMS-system

The purpose of the VMS-system is to enable information to be conveyed to the users

of the Expressway about speed restrictions and about special /dangerous weather

and traffic conditions, thereby ensuring a high level of safety and service for the

users of the Expressway, even in case of adverse weather conditions and incidents

on the Expressway. RTTMC shall also be able to activate the VMS with speed limit

information for other reasons than strong wind, e.g. in case of broken down vehicles

waiting to be towed, lost goods etc.

2.4 Central Control and Monitoring System (CCMS)

In general, the CCMS shall collect, store and present data collected from electro-

mechanical and traffic management installations, which shall be established on the

Expressway. The CCMS system comprises the following elements:

CCMS hardware and software

Control room equipment

2.5 Conclusions

The RTTMS is advances system of traffic management for Expressways which is

functional on many expressway in bits and pieces. A full-fledged system with

automatic control is needed for efficient and safe management of expressways.

Documents

Expressway Traffic Managemnt1