This map shows the section of the M4 that is frequently congested, and that would be bypassed if plans for a 14-mile relief road went ahead.
The Welsh government has long pushed for a relief road in this area. Plans were shelved in 2009 after the projected cost of the project rose to £1 billion.
More top news
Heavy showers set to spread into western areas tomorrow.
Andy Murray is Britain's last hope of a 2015 Wimbledon win after overcoming an apparent shoulder injury to beat Italy's Andreas Seppi.
New Tour de France time-trial record set after Australian Rohan Dennis raced into the lead during Stage one of the competition.