Car shutting off when tank is at 1/4 full

You lose power steering and power brakes because the engine died, and both of those features are powered by the engine, so those are side affects from the real problem, which is the engine dying at 1/4 tank of gas. You may have a fouled fuel pump or fuel filter, too much gunk in the tank getting sucked into the pickup screen on the pump. Or the problem is with the vent or purging of the tank, which are part of the EVAP system. If that is the case you may have some stored trouble codes. Try getting those codes read, most auto parts stores will do this as a free service. In addition to checking trouble codes, have the fuel pressure tested and EVAP system checked.

thanks i will look into that - i just thought it was a safety feature that makes you keep the tank full - because it is used for handicapped people and it should not run out of gas..

No way would having an engine stop dead on a highway be a safety feature. How would that be any different than just running out of gas in the first place? Again most likely a problem with fuel pump, fuel filter, or EVAP system. You don't mention other symptoms such as rough running, hard starts, or check engine lights, so I would focus on fuel pump/filter. A shop can test fuel pressure and give you advice.