Motorways are often some of our most Safe System aligned roads from a civil infrastructure perspective.
They usually have continuous barrier systems, no side impact intersections with poor angles, grade separation, and limited interaction between vulnerable road users and high speed traffic. From an infrastructure point of view, they are generally built to a very high standard.
But that alone is not enough.
The Safe System was never about relying on one layer of protection. Redundancy is important. When one part can’t address a crash cause or severity, another part needs to step in. Safe roads, safe speeds, safe vehicles, and safer road use all need to work together.
There will also be a lag while the vehicle fleet becomes more advanced. Technologies like AEB, blind spot warning, and other driver assistance systems will help, but they are not instantly everywhere. We are managing a mixed fleet for a long time yet.
Research by Elizabeth Hovenden, Hendrik Zurlinden and John Gaffney found that 53% of motorway casualty crashes were rear-end crashes, with another 18% being side swipe crashes. But they were heavily concentrated in the periods just before and during flow breakdown. So the video below is not a common crash scenario.
They also found managed motorways, with coordinated ramp metering across all ramps, had lower casualty crash rates than unmanaged motorways.
The reason was smoother traffic flow. Less speed variation, fewer stop-start shockwaves, less sudden braking, and fewer last-second lane changes.
Sometimes the best safety treatment is not more concrete. Sometimes it is better management of the system that is already there.
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Check out the research: