Three engineers and a brake failure

Three engineers sit in a car going downhill. A civil engineer, a mechanical engineer and a software engineer.

The brakes fail and the car narrowly avoids a very bad accident.

When it finally comes to a stop the civil engineer says "We got really lucky, that hill has a 15% gradient".

The mechanical engineer says "We should fix the brakes".

The software engineer says "We should do it again to see if the brakes will fail again."