Most of the forces involved PRIOR to the crash have been well understood for a long time.
Although there are still small changes to be made the scope for improvement is limited.
The problems are the limits of traction between rubber and road. If we improve the traction we make tyre life less and fuel economy worse so there is not a lot that can be done in this direction.
There have been efforts in stability control and in antilock braking. Both of which are designed to compensate for poor driving/poor judgment with a computer taking over the control of the car at critical moments.
Basically to prevent incorrect forces being applied to the wheels at the wrong moments.
Road design is primarily about making surfaces, and corners less severe so that it takes less control to travel along a road safely.
It also includes visibility to increase the time available so that a driver needs less skill to avoid a dangerous situation.
All of these are ongoing and could not rightly be called research.
Car design has included progressive crumple zones. By letting certain parts of the car bend in a collision it reduces the forces in other parts of the car making a collision more survivable.
And air bags which spread the forces more evenly over more of the body thus reducing the force on any one part which lessens the amount of injury for any given deceleration of the car in an accident.
All of the above can be summarized as, decrease the risk of a serious situation, decrease the risk that a serious situation becomes and accident then reduce the consequences of an accident.
Other classes of research are economic ones. We know many things that can reduce the risk of death and injury but they are too expensive. If we can find ways to reduce the costs then we can implement more of them.
Some other investigation is into anti tailgating devices that protect a driver from foolishly driving too close to a vehicle in front. And taking earlier avoiding action if the driver in front needs to modify their behaviour. This gets rid of the time delay of the bodies reaction and it also makes more precise judgments than a human might.
Legislative changes have often been investigated but rarely implemented because of an unwillingness of the population to make changes that may improve road safety. Collectively these changes could be summarized as reducing the probability that a situation would develop where a collision is likely.
Investigation has been done into the visibility of vehicles but again buyer resistance prevents these improvements being implemented.