Highway safety evaluation
Road Safety Audits (RSA) is a tool used for improving highway safety by reducing road accidents. The United Kingdom was a pioneer in using the concept of RSA, and it evolved in the eighties from the belief that road accidents, especially severe ones, can be avoided by adopting designs that are sensitive to road safety.
PIARC (Permanent International Association of Road Congress) has framed guidelines stating that RSA is required during all five stages involved in road construction: during feasibility studies, the preliminary design stage, the detailed design stage, pre-opening, and post-construction.
Conducting RSA for an existing road, where traffic is already in operation, is referred to as the reactive approach of conducting RSA. This approach involves identifying accident-prone locations, diagnosing the problems of these locations, assessing short-term and long-term remedial measures, and implementing these measures. All of these are covered under the reactive approach. On the other hand, the proactive approach of RSA involves adopting measures to prevent problems before they lead to accidents. Road Safety Assessment (RSA), which begins at the planning stage, and Road Safety Audit both fall under proactive methodologies.
The sequential steps in conducting an RSA start with the identification of a road or road network. It includes selecting a team of competent personnel, a pre-audit meeting between stakeholders, field inspection, and review by the RSA team to submit findings. The next steps involve analyzing the findings, discussing the analysis with clients, and incorporating the audit findings by revisiting the design approach and methodologies.
Adherence to compliance against National Standards is not sufficient, as sometimes standard designs at certain locations are not safe. It is important to remember that pedestrians and motorcyclists are the most vulnerable road users and are especially prone to traffic accidents.
During the planning stage, careful consideration needs to be given to points like cross sections of the road narrowed to minimize land acquisition, the probability of high speeds in pedestrian/habitation areas, U-turns, and median barriers that may block pedestrian movement. Tactile paving is necessary at signalized crossings to facilitate pedestrian movement. The design volume, traffic characteristics, typical cross sections, and variations need to be studied by expert professionals of the RSA team.
Field inspection and review are key considerations at the planning stage. The road network’s effects, general geometric standards, and proper provisions for pedestrians and motorcyclists must be studied in detail. For this, adequacy of lane widths, left and right shoulder widths, roadside clearances, median widths, and the consistency of the cross section are some of the important points of consideration during the field study and review.
Traffic calming features are necessary, and to achieve this, speed management, a safe systems approach to ensure non-motorized user safety, and performance-based practical design are essential. Traffic splinter islands on approaches to roundabouts and crosswalks in habitation areas may help reduce fatalities. In pedestrian areas, the speed should be restricted to the desired target speed. It has been observed that accidents increase when there is a significant speed difference between vehicles. Occupants of light vehicles sustain more severe injuries than those of heavy vehicles. For example, when a pedestrian is hit by a car, the severity of injuries is least when the car is moving at 30 km/h. Higher car speeds result in more severe accidents or fatalities. Research has shown that increasing speed by 1 km/h results in approximately a 3% increase in fatal accidents on a road with a speed limit of 50 km/h.
Examples of road engineering measures to reduce speed include speed humps, roundabouts, and raised crossings for pedestrians. On wider roads, intersections are sometimes set up with median islands that provide refuge for pedestrians, allowing them to cross in multiple stages.
Roadside hazards, such as fixed objects, trees, or utility poles, act as catalysts in aggravating the severity of accidents due to vehicles running off the road. Recently, tunnel safety has become a topic of discussion to prevent accidents involving vehicles moving through tunnels. Tunneling work is being carried out in rail and road projects worldwide. The role of a geological expert in the RSA team cannot be overstated, as the quality and cover of rock, the geometry of geological structures, groundwater pressure, and the permeability of rock masses all need to be studied in detail to avoid future risks. Considering the importance of geological features in hilly terrain, the inclusion of a geological expert in the RSA team is highly desirable.
