Forgiving Roads: How Infrastructure Eliminates Crash Impacts in the Safe System Approach

For years, the traditional perspective on traffic safety tended to place the blame solely on driver errors. However, throughout my many years in the industry, there is a clear reality I have seen in the field and in international projects: Humans inherently make mistakes. Fatigue, momentary distraction, an incorrect maneuvering decision or a sudden reaction reflected in the vehicle telematics data... These are part of being human. The real issue is whether these mistakes will have a fatal cost when they result in a crash.

This is where modern engineering comes into play. The Safe System approach accepts the human potential to make mistakes and designs the system according to this reality, namely, to protect humans.

The Unforgiving Rules of Physics and Kinetic Energy Management

To fully analyze exactly what happens during a crash, we must delve into the very foundation of engineering, which is physics. A vehicle's mass and speed determine the kinetic energy that will be released:

In this formula, the velocity is squared. Therefore, a minor breach of the speed limits exponentially increases the energy that the human body will be forced to absorb during a crash. The human body lacks the biological structure to tolerate high kinetic energy within an environment consisting of steel and concrete. The primary objective of the Forgiving Roads concept is to absorb this energy through infrastructure elements before it ever reaches the human body.

Rating Roads with iRAP and ViDA Analysis

How do we objectively measure how well a road design can manage this energy? Here, the International Road Assessment Programme (iRAP) standards provide us with a global language. Detailed analyses conducted through the ViDA software create a multidimensional risk map by dividing the road network into short segments.

• 1 Star Roads: These are the riskiest segments that leave no margin for error, where roadside obstacles (trees, concrete poles, unprotected culverts) are at the zero point of the road, and which contain unprotected intersections. The cost of a simple steering error on these roads is very heavy.
• 3 Star Roads: This is the acceptable minimum engineering level that meets basic safety standards, featuring appropriate barrier systems and clear lane markings.
• 5 Star Roads: These are exemplary structures providing physically separated lanes, wide and unobstructed shoulders, smart intersection designs where speed is managed naturally, and full protection for pedestrians. The goal is always to minimize risk by increasing the number of stars.

World Bank ESS4 Standards and Vulnerable Groups

Road infrastructure cannot be designed solely for motor vehicles or fleets. The Community Health and Safety criteria we evaluate within the framework of the World Bank Environmental and Social Standards (ESS4) mandate the protection of the ecosystem and human life surrounding road projects. Particularly in rural crossings or routes dividing settlements, vulnerable road users such as pedestrians, cyclists, and the elderly must be placed at the center of the project. Infrastructural measures to be taken during a road operation process must protect everyone crossing that road from a potential crash risk.

The Core Engineering Components of Forgiving Road Design

Clear Zones

These are safety areas cleared of trees, concrete poles or hard rocks that provide the driver with a chance to recover the vehicle in the event of leaving the road.

Energy Absorbing Guardrails

These are smart systems that absorb kinetic energy by flexing during a crash and redirect the vehicle back to its own path without allowing it to roll over or cross into the opposite lane.

Roundabouts

They specifically prevent right angle crashes at four way intersections. Their geometry inherently forces a reduction in speed and even if a crash occurs narrowing the impact angle prevents the energy from reaching fatal levels.

Crash Cushions

These are placed in front of unavoidable fixed obstacles such as highway entrances, toll booths, bridge and viaduct pillars. By folding like an accordion or bursting the water or sand inside during a crash, they gradually absorb the energy and prevent the vehicle from stopping abruptly.

Vulnerable User Segregation

These are physical islands, raised crossings, and independent corridors that prevent pedestrians and cyclists from encountering motorized traffic on the same plane.

Motorcycle Protection Barrier Systems

The exposed posts of standard guardrails that make contact with the ground turn into fatal obstacles for motorcycle riders during an asphalt slide or a direct crash. Forgiving road infrastructure mandates the use of continuous and flexible attachments (rub rails) that close the bottom gaps of the barriers to minimize this risk. These lower rails prevent the rider from directly striking the posts or going under the barrier; they absorb the kinetic energy and allow the body to decelerate by sliding safely along the barrier. Especially in sharp curves with blind spots and high speed highway entrances this engineering touch is the most critical lifeline for two wheeled road users.

Rumble Strips

These are surface applications that come into play when a driver drifts out of the lane due to fatigue microsleep or cognitive distraction. When the tire makes contact with these strips the intense vibration and sound created alerts the driver proactively preventing the vehicle from leaving the road.

Conclusion

If we want to permanently transform the road safety culture we must shift our focus from the utopia of creating a perfect human who never makes mistakes to building perfect systems that protect humans. Adopting this vision in every field from corporate fleets to public projects is the only valid way of a sustainable road safety policy.