Slaughter Mountain Run (1990)

From the back of the book

America, 2020 A.D. Eight years ago the terrorist agents of H.A.V.O.C. triggered a nuclear nightmare that devastated the northern hemisphere. A few lucky survivors escaped the radioactive aftermath in underground colonies, waiting for the day they could rebuild their shattered world. That day has come...but the real battle for survival has just begun!

You are Cal Phoenix, the freeway warrior, champion and protecor of Dallas Colony One. Your convoy of survivors is on its way o El Paso, hundreds of miles away beyond he West Texas wasteland. But before your exodus can continue, a dangerous mission must be completed: to rescue Kate Norton, who's been kidnapped by H.A.V.O.C. terrorist leader Mad Dog Michigan. You must save Kate and rendezvous with the colony...and you have only seven days to do it.

This mission will require all your strength and skill for success - and survival!