At a time when people suggest the speed limit on motorways could be increased due to safer vehicles and better braking this happens.
Temporary 50mph speed limits on two stretches of the M4 - introduced to cut air pollution through built-up areas - are to be made permanent.
The limit was reduced on the motorway and on stretches of A-road in December 2018 in an attempt to cut nitrogen dioxide emissions.
The Welsh Government has now confirmed the restrictions will stay permanently.
The 50mph limits are at the M4 Port Talbot, M4 Newport, A470 Pontypridd, A483 Wrexham and A494 Deeside.