Proper signing has an important part in speeding allegations, an analysis of this invloves asking whether the signs erected at the location provide adequate guidance to the motorist.
There is a statutory duty on the Secretary of State to erect and maintain traffic signs to provide such guidance in relation to motorway and trunk roads, and on the local authority in relation to other roads.
The law on road signing is largely contained in the Traffic Signs Regulations and General Directions 2002 and contains detailed provisions relating to the position, and contemporaneous content of signs.
As a general observation, if a driver considers the signing to be inadequate the Court will be greatly helped in determining the issues if there are photographs showing what was visible to road users. There may be issues over obstruction or position contemporaneous photographs and a plan can be a significant help months later when a case comes for hearing.