All traffic counters for the N20 lie within the Limerick and Cork metropolitan regions, with the exception of Rathduff. The Rootiagh and Raheen counters lie on what is now the M20, redesignated in 2009, and are showing high levels of Limerick commuter traffic. The Croom counter, lying after the N20/N21 split, shows a far lower level due to the division of traffic streams.
Down south in Cork, Blackpool shows a high count and marks the end of the current dual carriageway section. The need for an extension northwards is certainly apparent judging from the high count at this point, which peaked at 24,000 in 2007. Even Rathduff, 18 km out, was up to 18,000.