In California, for instance, the Vehicle Code required drivers to not exceed 15 mph within 100 ft of an unsignaled railway grade crossing. While street running is a less common form of a grade crossing, its hard to claim that it is not
The prima facie limits are as follows and shall be applicable unless changed as authorized in this code and, if so changed, only when signs have been erected giving notice thereof:
(a) Fifteen miles per hour:
(1) When traversing a railway grade crossing, if during the last 100 feet of the approach to the crossing the driver does not have a clear and unobstructed view of the crossing and of any traffic on the railway for a distance of 400 feet in both directions along the railway. This subdivision does not apply in the case of any railway grade crossing where a human flagman is on duty or a clearly visible electrical or mechanical railway crossing signal device is installed but does not then indicate the immediate approach of a railway train or car.
So a vehicle is required to be going no more than 15mph by the above, and then must stop when they see a train (or hear a bell or horn) ...
CHAPTER 8. Special Stops Required [22450 - 22456] ( Chapter 8 enacted by Stats. 1959, Ch. 3. )
(a) The driver of any vehicle or pedestrian approaching a railroad or rail transit grade crossing shall stop not less than 15 feet from the nearest rail and shall not proceed until he or she can do so safely, whenever the following conditions exist:
(1) A clearly visible electric or mechanical signal device or a flagman gives warning of the approach or passage of a train or car.
(2) An approaching train or car is plainly visible or is emitting an audible signal and, by reason of its speed or nearness, is an immediate hazard.
So, if the vehicle gets hit by a train, the vehicle driver has already broken the law.