From a comment in a website
"I am Jeddah I asked the same questions about women not allowed to drive.
The answer was clear from Saudis they said it is not a religious restriction, we restrict because we don’t want our women to fall in unnecessarily interaction with strangers and they themselves say there are some monster in society who may harm the women when met with a accident. Also they say that Saudi is land with 8million expats and most of them living without their family and they want this rule for they safety and for the goodness of their women."