There is an excellent modern multi lane highway from Jeddah. During the Hajj pilgrimage season it is jammed with buses full of pilgrims. At any other time, traffic is extremely light for the size of the road.
A few miles outside Mecca, there is a cutoff referred to as the "Christian bypass". Turn along this highway to drive another 50 miles out of the way to reach the lovely mountain town of Taif. Taif, at 5000 feet elevation, was the former summer palace of the Saudi Kings. If you remain on the main highway, there is a police checkpoint just after the exit, where non-Muslims are kept out of the holy city.