The M45 is a spur from the M1 in Northamptonshire, westward towards Coventry. Today it just provides access to part of Coventry from one direction on the M1, but its historical significance is much greater.
A first step towards emissions-based road pricing, a pointless measure to enforce something that's happening anyway, or another leap forward in traffic planning from the people who created the Congestion Charge? It's hard to say.