The recent launch of the M42 hard shoulder running pilot has created a measure of public disquiet even if it has not always been well informed.
The hard shoulder is there for a reason and any scheme that removes it needs to be able to maintain some place of refuge for drivers who break down, and provide access for emergency vehicles.
At this early stage, the M42 pilot looks as though it manages to do this. It can provide whichever of an extra running lane or a traditional hard shoulder is most needed, and is able to change between the two safely.
But to do this it needs vehicle detectors and overhead gantry signals which allow traffic control (including speed limits) in each individual lane. It also needs the mass deployment of CCTV cameras, and the construction of emergency refuges beyond the hard shoulder at about 500m intervals. All in all this brings a bill of getting on for £100M.
There are places away from the M42 where the hard shoulder has safely been turned into a traffic lane - for example on the approaches to slip roads. For these short distances we can cope without a hard shoulder, as we do for some bridges on widened motorways. At motorway roadworks, the hard shoulder often becomes a traffic lane that keeps traffic flowing, but with 24 hour free removal of broken-down vehicles.
Today it looks as if sophisticated traffic information and management technologies can make hard shoulder running possible without impacting on safety, but only on short sections of motorway, at limited times and as a tactical short term measure.
But the £100M bill for the M42 must look big to many. Plans are already being made to dispense with the hard shoulder altogether on other motorways, and we have to have serious reservations about this.
While we must be pragmatic, and seek out new workable solutions to increasing traffic congestion, safety must not be traded for extra capacity.
The M42 has been the subject of a huge education campaign. But there is a limit to the number of hard shoulder running arrangements that can be used without confusion.
The M42 has gantries and hard shoulder running. The western M25 has gantries but no hard shoulder running. The next scheme may just have hard shoulder running and no gantries, while the other motorways will still have neither gantries nor hard shoulder running. We uniform and easily understood rules.
We have welcomed the closely monitored trial on the M42. But we have also told the government that taking away the hard shoulder can only be a short term solution.
The M42 pilot could yet become an expensive culde-sac in the development of motorways in the UK, while the way ahead becomes the cheaper option of permanently dispensing with the hard shoulder. At the moment it looks as if this is a serious possibility. This must not be allowed to happen.
Andrew Howard is the AA Motoring Trust's head of road safety