 The first section of the PDR to be completed was the Southern Way Link Road in 1978 and the last section was the Butetown Link Road in 1995 . Construction of the first phase of the final link road , the Eastern Bay Link Road , started on 17 March 2016 and is due to be completed by April 2017 . When fully completed , the road will form part of the Cardiff ring road system . The PDR runs west , south and east of Cardiff , with the M4 between junction 30 and junction 33 completing the northern section . The PDR is dual carriageway for its entire length except for the East Moors Viaduct , which is a single carriageway . 
