Simplify the following text for a Grade 8 native English-speaking person.
Original: Brakes are used on the cars of railway trains to enable deceleration , control acceleration ( downhill ) or to keep them standing when parked .
Simplified: Railway brakes are brakes which are used for the cars of railway trains . The brakes are used to enable deceleration , to control acceleration when going down slopes or hills and to keep the cars standing while they are parked .