FURTHER to the letter from A L Dixon, (Box too big, March 31) the yellow box road markings are not legally enforceable at the Tadcaster Road/Moor Lane and Clifton Moorgate/Stirling Road roundabouts.

Rules governing road signs/markings on the highway (Traffic Signs Regulations & General Directions 2002) state: "Road markings... shall not be placed to indicate an area of carriageway on a roundabout unless the entry of traffic is at all times controlled by traffic light signals".

And from Chapter Five of the Traffic Signs Manual, the reason why yellow-box markings are not used on roundabouts unless the roundabout is signalised at all times: yellow box markings are prohibited at unsignalled intersections on roundabouts because a circulating vehicle has priority over those entering. If it stops to avoid obstructing the box when its exit is blocked, thereby releasing the flow of entering vehicles, there is likely to be uncertainty over re-establishing right of way when the exit is clear again.

Moreover, a vehicle stopped in an outer lane might obscure vehicles lawfully continuing to circulate on the inner lanes (whose exit might not be blocked) from the view of drivers entering the roundabout. Yellow box markings may however be used where traffic entering the roundabout is controlled by signals at all times.

Given that the Tadcaster Road roundabout isn't controlled by traffic signals at all times but has Pelican/Toucan crossing points on the approaches, and Clifton Moorgate is completely uncontrolled, these markings are illegal.

I have asked City of York Council to remove the road markings from the Clifton Moorgate roundabout and received a reply from Peter Evely recognising the road markings are not enforceable.

Strange that the City of York Council spokesperson doesn't mention this fact.

Peter Ward (MIHE), Portal Road, York.