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
Foreign criminals are costing the UK £850m, with the number jailed or deported remaining broadly unchanged since 2006, according to a report
Toys R Us has scrapped its four collectible dolls based on the characters of the hit TV series Breaking Bad after a campaign by a US mother
Late actress Lynda Bellingham shared how she planned to spend Christmas during a moving final interview on Loose Women to be broadcast later