expressway traffic managemnt1
TRANSCRIPT
-
8/4/2019 Expressway Traffic Managemnt1
1/14
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
-
8/4/2019 Expressway Traffic Managemnt1
2/14
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,
-
8/4/2019 Expressway Traffic Managemnt1
3/14
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.
-
8/4/2019 Expressway Traffic Managemnt1
4/14
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
-
8/4/2019 Expressway Traffic Managemnt1
5/14
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.
-
8/4/2019 Expressway Traffic Managemnt1
6/14
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
-
8/4/2019 Expressway Traffic Managemnt1
7/14
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
-
8/4/2019 Expressway Traffic Managemnt1
8/14
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
-
8/4/2019 Expressway Traffic Managemnt1
9/14
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
-
8/4/2019 Expressway Traffic Managemnt1
10/14
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
-
8/4/2019 Expressway Traffic Managemnt1
11/14
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
-
8/4/2019 Expressway Traffic Managemnt1
12/14
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.
-
8/4/2019 Expressway Traffic Managemnt1
13/14
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.
-
8/4/2019 Expressway Traffic Managemnt1
14/14
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.