ANOTHER VEHICLE CUT IN FRONT AND BRAKED FOR RED LIGHT CAUSING ME TO "LOCK UP" THE BRAKES. THE TRUCK HAS REAR ABS WHICH KEPT THE REAR WHEELS FROM "LOCKING UP". VEHICLE ACCELERATED DURING HEAVY BRAKING WHICH CAUSED THE COLLISION. ABOUT 50 FEET OF BRAKE MARKS WERE LEFT ON THE ROAD SURFACE FROM THE FRONT TIRES. IN A SEPARATE INCIDENT, A VEHICLE SUDDENLY MERGED FROM LEFT SIDE OF ROAD CAUSING ME TO SWERVE TO THE SOFT SHOULDER ON THE RIGHT. TRUCK HAD COME TO A COMPLETE STOP WHEN THE RIGHT REAR WHEEL STARTED TO SPIN. IT SPUN FOR ABOUT 10 SECONDS BEFORE IT STOPPED. TIRE DUG INTO THE SOFT SHOULDER AND LEFT A SPRAY OF DIRT BEHIND THE TRUCK.. HAVE BEEN SEARCHING FOR A FACILITY TO TEST THE BRAKING SYSTEM. IT APPEARS RELATED TO THE STALLING WHILE STOPPING PROBLEM.