Of course the key difference between roads and railways is that railways are a completely closed system. Network Rail know what the capacity is, and they allow the TOCs to run a specific number of trains to fill that capacity. The TOCs publish the timetable, and contract with their customers based on that timetable.
If the railway shove too many trains on a line or fail to staff them properly, then the argument goes that they should have known better and as a result, and as a result it's reasonable to expect compensation paid to the customers who have contracted according to a timetable. If too many people use the road at some given time, well that's kinda their own fault given that a vast amount of information is available to help people choose the best time to travel.
If there is an incident on the railway, then the argument goes that it is a closed system - it is or should be a secure environment where Network Rail's responsibility is to keep out external influences and manage the system so that it runs optimally in any given scenario. Anyone and anything permitted on the railways must meet extremely strict criteria, defined by Network Rail to ensure safety and optimum running. Therefore if they fail to do that, it's reasonable to expect compensation. The roadways are not a secure environment. Anybody can use them, using almost any method and there is almost never anything stopping them. There are published requirements for minimum safety standards, but individual drivers are responsible for meeting them on a day to day basis. In an open system, it's unreasonable to expect compensation if you are delayed because something that can't be stopped has happened.
Potentially, the only similarity that could be argued is that if Highways England fail to maintain the roadways in poor weather compensation might possibly be due, but it would probably be unreasonable given that there is no way to know who would or would have been travelling and the cost of any such scheme would be insane compared to any benefits... It's just not practical in an open system.