Modern LRVs (and BART-type electric MUs) use 100% dynamic (wasted thru grids) or regenerative (back to the wire) braking down to less than 5 mph where the friction brakes take over, for normal brake applications. For full-service or emergency braking friction brakes (acting on more than just the powered axles) are added. Very recent models also seem to have "anti-lock" systems that in normal braking may add sand or adjust braking power distribution automatically to avoid sliding. In addition, most have a magnetic track brake (simply on or off) for added stopping power and (if I recall PCCs in SF correctly) holding the car when stopped with the doors open. You can feel the low-speed transition if the driver is braking moderately. Most Siemens/DuWag-pattern LRVs have only one axle powered under each end of the car, so adhesion for the dynamics can be a problem when heavy braking is needed. The friction brakes might be air, but most LRVs at least seem to be all-electric these days (though on trips Back East I have noticed more air-braked stock (by sound) than we have Out West).

Hybrid & electric cars work very similarly, though with the limited electric power available in a hybrid and limits on how fast the battery can recharge, friction brakes combine with regen more often.

As noted in various threads recently, transit practice probably doesn't carry over much if at all to Standard Railroading.