The half-term getaway has caused 40-mile tailbacks along parts of the M5.
Motorists travelling along the southbound stretch of the road around Bristol, Somerset and Gloucestershire were hit with "severe delays", traffic monitoring website Inrix said.
It said: "Slow traffic due to holiday traffic on M5 Southbound between J14 B4509 (Thornbury/Falfield) and J21 A370 (Weston-super-Mare). Patchy delays."
Motorists were advised to use alternative routes if possible.