The design of roads, including road bridges and tunnels, on the national road system is a matter for the National Roads Authority under the Roads Act 1993. The NRA Design Manual for Roads and Bridges is also applicable to non-national roads. Arrangements are being made to introduce a statutory maximum vehicle height limit of 4.65 metres.
As with the Dublin Port Tunnel, the planned Limerick Tunnel will have a height of 4.65 metres. No other road tunnels are currently planned. Any supertrucks of a height of 4.65 metres or lower can be accommodated under any of the two existing tunnels and in the Limerick Tunnel which is under construction.