GMC 1995 Safari Owner's Manual page 106

This light should come on briefly as you start the vehicle. If it doesn't come
on then, have it fixed so it will be ready to warn you if there's a problem.
If the light comes on while you are driving, pull off the road and stop
carefully. You may notice that the pedal is harder to push. Or, the pedal may
go closer to the floor. It may take longer to stop. If the light is still on, have
the vehicle towed for service. (See "Towing Your Vehicle'' in the Index.)
The brake system warning light will also come on when you set your
parking brake, and it will stay on if your parking brake doesn't release fully.
If it stays on after your parking brake is fully released, it means you have a
brake problem.
Anti-Lock Brake System Warning Light
Standard Cluster
. - -
Digital Cluster
With the anti-lock brake system, this light will come on when you start your
engine
and
may stay on for several seconds. That's normal. If the light
doesn't come on, have it fixed so it will be ready to warn you if there is a
problem.