Delays at new traffic lights.
The new system at the Sycamore Cross junction of the Five Mile Lane, in Barry, was switched on last Friday in a bid to improve safety.
But motorists have complained that the new system has led to hold-ups of up to 20 minutes at busy times.
Traffic managers with the Vale council say that the system will now be closely monitored and, if necessary, the timings will be adjusted.
The junction improvement works were funded by the Welsh Government as part of the National Transport Delivery Plan 2012-13.