Principles-procedures and practices in road design

 SAFETY IN ROAD DESIGN

Principles

Accident reduction and accident prevention are the two main strategies in road safety.  The construction of the road network and the road design have a large effect on road safety. Accident prevention is the application of expertise in safe road design. This primarily involves road geometry as well as the materials used. A road is considered safe when there are NO ACCIDENT occurs. Below are listed a few important principles involved in design of safe roads.

• Physical separation of driving direction, separate cycle lanes
• Roads should be designed as per their functionality, i.e, service road, access road as a hierarchically structured road network
• The roads should be designed so that there is equality in speed, direction and mass at medium and high speeds
• The road should be designed such that it should minimize injuries in case of accidents by anticipating behavior of road users
• Roads and roadsides should be designed such that they are predictable and forgiving of mistakes
• The roads should be designed for travel speeds that suit the function and level of safety of the road
• The roads should be designed to prevent crashes and protect road users
• Provision should be made for the main supporting system elements like
• Emergency medical management
• Effective legislation and systems, enforcement and justice support systems
  

  Procedures

 Few of the procedures used by engineers to keep roads safe are

• Installing barriers
• Separate oncoming traffic
• Prevent vehicles from veering off the road and causing serious injuries
• Protect construction workers and pedestrians 
• Types of barriers
• Guard rail barriers
• Traffic cones
• Concrete barriers
• Steel cable barrier
  
• Setting speed limits for roads
• In April 2018, the Union Ministry of Road Transport and Highways fixed the maximum speed limit on 
• expressways at 120 km/h, 
• national highways at 100 km/h, 
• for urban roads at 70 km/h
  
• Installing traffic lights and signs at intersections and accident hotspots
•  An engineering solution for improving traffic safety performance is installing traffic lights
• Software specialising in road safety helps in identifying accident hotspots based on historical accident data
• Other techniques used for safe road design involve
• Repainting road markings
• Intersection channelization
• Drainage optimization and
• Sight distance improvement

Effectiveness of these solutions has been evaluated by Empirical Baye's (EB) models and an improved traffic safety performance has been observed by reduced crash occurrence risk and crash severeties.

 Practices 

•  Roads in India have a heterogeneous mix of traffic. Space occupied by each of these vehicles, acceleration and deceleration characteristics and possible maximum speeds by each user is variable. Hence, space allocation to different vehicles should be carefully ensured to ensure a smooth and safe flow of traffic.
• The type and character of each type of road (mobility or access or both)  should be carefully studied in detail. Appropriate geometric design standards is essential to ensure safety to all road users
• Design of entire road cross-section is important as it governs design speed of vehicles and reflects prioritization in space allocation and introduces the concepts of universal design and traffic calming
• Road markings are essential to guide road users and ansure a smooth flow of traffic