The route has been closed since February following a landslip.
Now Mike Watts has set up the Kelston Toll Road across fields surrounding the closed stretch of the A431.
Watts has spent £150,000 building the new 400 metre toll road and is charging motorists £2 a time to use the route.
The road has toll booths at each end and offers drivers an alternative to using a 16km diversion with repair work on the A431 not due to finish until Christmas.
Skanska is currently carrying out the £2m repair works to the damaged stretch of the A431
The toll road is open: pic.twitter.com/grbK5HElL8