ROAD DESIGN FOR BETTER SAFETY Abdul Rahman Baharuddin Public Works - - PowerPoint PPT Presentation

Abdul Rahman Baharuddin Public Works Department Malaysia

ROAD DESIGN FOR BETTER SAFETY

PIARC International Seminar and Workshop on Safer Roads by Infrastructure Design and Operation 2019 Berjaya Times Square Hotel 23-25 April 2019

CONTENT OF PRESENTATION

• 1. Road Traffic Safety
• a. Facts about Road Safety
• b. Safe Operation of Roads
• 2. Accident Causation Factors
• a. Human Factors
• b. Vehicle Factors
• 3. Principles of Design for Safety
• 4. Conclusions

ROAD TRAFFIC SAFETY

Engineers design roads to protect people and get people to their destination in a timely manner. However, mishap can happened resulting in injuries and fatalities. Fatalities due to road traffic accident are largely avoidable and for large part of world’s population road death is the highest fatality risk. Road traffic safety is the process of reducing the risk of a person getting injured while using roads. Road design incorporating safety aspects must help the motorist understand what to do and forgive driver errors when they happen and these should eliminate a large proportion of these fatalities.

Facts About Road Safety

1.35 million people died due to road traffic crashes every year Road traffic casualties cause considerable economic losses to individuals, their families, and to nations as a whole. Road traffic crashes cost most countries 3% of their gross domestic product. More than half of all road traffic deaths are among vulnerable road users: pedestrians, cyclists, and motorcyclists. Road traffic injuries are the leading cause of death for children and young adults aged 5-29 years.

Safe Operation of Roads

ACCIDENT CAUSATION FACTORS

• Human behaviour

contributes to 95% of crashes.

• Roadway discrepancies

contributes to 28% of crashes.

• Vehicle failures

contribute to 8% of crashes.

Human Factors

Human performance failure involved in more than 90% of road accidents In many cases road users are often faced situations where the 'driving' task exceeds reasonable human capabilities. Human performance characteristics which are important in road and traffic engineering are…

• Vision - visual perception, ability to see
• Information needs - the information required
• Information processing - the process involved from the start of receiving

information till the action executed by the driver

• Human Vision

Very important factor as it covers 90% of driver’s information need. Designers must know the important characteristics of human eyes.

• Human Vision

Field of vision consist of peripheral vision and the central vision... Field of vision reduces as speed increases. This fact is important in the positioning of traffic signals and signs. Designers must recognised that not all road users have perfect vision. Design for 6/12 vision for 95% pop.

• Information Needs

Recognising the road users visual capabilities and limitations. Understanding the information drivers need to operate their vehicle safely. Most information are based on visual and must be made easily understandable to all road users. Need to comply certain criteria...

• Information Needs

➔ Conspicuity - easily seen against its background ➔ Comprehensibility - can be quickly understood and its importance recognised. ➔ Credibility - must be believed to be true and relevant to road users at the time.

Well established, consistently used standards and practices

➔ Delineation - information for drivers to maintain vehicle position on the roadway,

guidance for short range and long range navigation

• Information Processing

This is the process involved from the time a driver receives an information until the execution of the necessary action. Drivers receives information, process it, make decision, carries out the chosen action and observes the result by repeating the process. This process can be complicated because of the limits of human performance and the difficulties imposed by the interface between the driver, the vehicle and the road environment.

• Information Processing

Important for designers to ensure road users can perform the tasks within their human capability. Reduce difficulty of driving task through the followings:

• Providing 'trend' Information...
• Avoid rapid and heavy demands from drivers...
• Allow for series of simple decisions rather than a single complex decision...
• Give quantitative rather than qualitative information...
• Control rate at which drivers are required to make decisions...

Other Human Factors

Expectancy Most driving behaviour is governed by habit, experience and expectation. Information presented in the expected form and with a logical sequence of events should result in drivers making less errors. Poor information does not match drivers expectation then accident are likely. Expectancy is enhanced by experience, similar situation that being treated consistently should result in less errors or misjudgements.

Other Human Factors

Reaction Time Involves Perception - seeing the sign or signal Identification - identify signal and understanding the meaning Emotion - deciding what action to take Volition - carrying out the action Varies and can take up time from 0.7 to 3.0 secs. Common average 2.5 secs. Sometime a duration of 1.5 secs is used. Improving the performance by minimise the alternative actions, provide positive info and prior warning to a situation

Other Human Factors

Short Term Memory Short term memory, information fades after about 30 secs... Info presented must be immediately applicable. Otherwise, it must be continually reminded. The rate of info need to be controlled so that one item can be dealt it at a time

Vehicle Factors

Vehicle factor - involved in small proportion of accident but there are many aspect of vehicle design and operation which are important for the design of safe road. Designers must realize the significance of some of the vehicle characteristics:

• Vehicle dimensions
• Visibility - driver’s view
• Braking - ability to stop
• Manoeuvrability - easily manoeuvred while in motion.
• Cornering - the ability of the vehicle to resist overturning and to utilise all of the

available side friction between the tyres and the road surface.

PRINCIPLES OF DESIGN FOR SAFETY

Intersection Design

Intersection Design

Layout

• Intersecting angle...
• Provision of turning lanes...
• Increase no of lane for capacity...
• Avoid seagull layout T junction...
• Evaluate the provision of free flow

slip/auxiliary lanes at signalised intersection...

Intersection Design

Conflicts

• Minimise number of conflict points
• Separation of conflict zones
• Reduce area of conflict zone
• Minimise angle of conflict

Intersection Design

Delineation

• Provide adequate direction, guidance

and signing…

• Guided path of travel...

Intersection Design

Traffic Lanes

• Avoid 'trap' lanes
• Separate slow moving or waiting traffic

from through traffic

• Segregate ‘unprotected’ road users

Kerb sidewalk for pedestrian Separate stopline for motorcyclists/bicyclists Dedicated lane for motorcyclists/bicyclists

Intersection Design

Visibility and Hazards

• Ensure good visibility to conflict

points…

• Provide adequate sight distance
• Minimise roadside hazards

PRINCIPLES OF DESIGN FOR SAFETY

Road Links Design

Road Link Design

Geometric

• Adopt appropriate geometric

standard for horiz and vert alignments...

• Ensure the appropriate sight

distances is being checked

Road Link Design

Cross Section

• Sufficient row width for flexibility in

layout design

• Lane width from 2.5m - 3.65m. Wider

lane for higher speed

Road Link Design

Access Control

• Provide access control in accord with

the road 's functional class and the nature of abutting land development…

• Provision of service road.

Road Link Design

Delineation

• Provide good delineation and street

lighting where warranted.

• Provide adequate traffic signs and

road markings.

Road Link Design

Roadside

• Provide a "forgiving" roadside

environment along the road...

Road Link Design

Speed Control

• Speed should be restricted at

accident prone areas...

• Set an appropriate speed limit

CONCLUSIONS

Design of safer road requires the recognition and understanding of human and vehicle factors and their characteristics. Principles for the design of road must incorporate all necessary safety elements. Design may have contributed to the road safety problems at first but it still has an important role to play in addressing the issues by putting it right and save life.

Thank You Terima Kasih

Don’t do the right thing first and then do the thing right but do the right thing right the first time every times!