Highway Safety

Methods Adopted By

Civil Engineers

Haider Ali JafferiCivil Engineer

The main purpose of adopting safety measures for highways and road sides is:• To reduce no. of accidents,• To facilitate safer journey,• To increase the quality of transit

system,• To maintain the regular traffic flow.

Introduction:

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• Cross Section• Rumble Strips• Design Of Roadside• Junctions• Linear villages• Roundabouts• Traffic calming road design• Innovative Interchange and

Intersection design• Traffic signs• Pedestrian Crossing• Barriers

The main elements of a road cross section are:

The pavement with the vehicle lanes, edge strip and markings

The emergency zone and obstacle free zone

The embankment and cutting slopes The width of the cross section is

determined by the pavement related to the number of lanes

The required width of the edge strip The shoulders and earthwork slopes

and depth

Cross section

To reduce the number and severity of roadway departure crashes, or run-off-the-road and cross center line crashes on 2-lane, rural, undivided roads.

Rumble Strips

Rumble Strips (cont)

Shoulder rumble strips: Placed on highway shoulders along the edge of the travel lane, to prevent single vehicle run-off-the-road crashes.

Center line rumble strips:

Placed on or near the center line, to prevent head-on crashes and opposite direction sideswipe crashes. They can also be helpful to prevent some crashes when a driver veers across the center line

Rumble Strips (cont)

Advantages: Alert drivers upon drifting or

deviation. The reflective paint helps to increase

visibility. Reduce the number of crashes.

Design Of Road-Side

Design of road side must comply the following essential requirements:

i. The road must be free from ditches and screeding should be done properly.

ii. Shoulders and edge strips must be provided.

iii. Super elevations must not be too steep.

Design of Road-Side (cont)iv. Avoid sharper turns.v. Emergency zones/lanes must be

provided.vi. Wider Obstacle free zones to reduce

the risk in case of road run-off accidents.

Junctions

“A road junction is a location where multiple roads intersect, allowing vehicular traffic to change from one road to another.”

Junctions (cont)

A road junction has to fulfill following requirements:

i. Visibleii. Oversee-able iii. Comprehensibleiv. Completeness

Linear Villages

“A linear village is that part of a (transit) road which lies within a built-up area.”

Passing a road from public areas must comply with the special safety needs:

i. Pedestrian Safetyii. Speed reduction measuresiv. Footpaths, side railings and

shouldersv. Avoid Sharp turns and blind corners

Originated in Europe over 35 years ago.

Intended to calm (or slow down) traffic.

Used primarily as a safety measure on low volume & low speed roadways.

Traffic calming may involve “physical changes" to the roadway that slow traffic down. Some examples:

Traffic Calming Road Design

Using innovative design interchanges & intersections to help move large volumes of traffic through limited amounts of space safely and efficiently.

Following are the main types:i. Diverging Diamond Interchange

(DDI)ii. Echelon Interchangeiii. Single Point Interchange (SPI)

Innovative Interchange and Intersection Design

Innovative Interchange and Intersection Design (Cont)i. Diverging Diamond Interchange (DDI)This innovative interchange, sometimes called a “double crossover diamond,” .

Innovative Interchange and Intersection Design (Cont)

Purpose: Increase capacity Safety Decrease

congestion Minimize the cost

of new infrastructure.

Advantages: Safety Greater

capacity and efficiency

Easy navigation

Suitability

Innovative Interchange and Intersection Design (Cont)

ii. Echelon InterchangeThis innovative interchange is designed to accommodate two high-volume streets. An echelon introduces a bridge, splitting traffic into two levels, creating two separated intersections of one-way streets. Because there is no opposing traffic for left turns there is more green light time for all movements.Advantages

Safety Greater capacity

and efficiency

Innovative Interchange and Intersection Design (Cont)

iii. Single Point InterchangeAll traffic is controlled by a single set of traffic signals located in the center of the intersection.

Innovative Interchange and Intersection Design (Cont)

Reasons for considering SPI: Better Safety Greater capacity and efficiency than

conventional designs Also accommodates large trucks. Ease of Navigation

Traffic Signs

Traffic signs or road signs are signs erected at the side of or above roads to give instructions or provide information to road users.

Traffic signs generally :• Control the flow of traffic• Warns about hazards ahead• Guide to destination• Informs roadway services.

Traffic signs are intentionally color coded to assist the operator.

In traffic signs, fluorescent material is used.

Various sign

boards are used, such as:

i. Stop & Yield Sign Boards

A STOP sign is a traffic sign to notify drivers to completely halt while YIELD means to slow down to at a point

ii. Warning Signs

Alerts to hazards or changing in conditions such as changes in road layout, proximity to a school zone, sharp turns etc.

iii. Guide signs

Indicates route markers, distance-and-destination signs, and informational signs.

iv. Construction & Maintenance Road Work Warnings The work areas are protected from

traffic by orange (or yellow) warning signs during the construction or repairing works.

Help to guide pedestrians and vehicle traffic safely through a work zone and past any hazards.

Roundabouts

“A roundabout is a type of circular intersection or junction in which road traffic flows almost continuously in one direction around a central point.”

Improved safety Due to Roundabouts