INSPECTION OF road drainage needs drastic improvement to stave off fears that another wet winter will waterlog the road network, a senior highways engineer warned this week.
Director at consultant Mott MacDonald, John Henderson, called for changes to the Highways Agency's maintenance guidelines, set out in the Road Maintenance Manual System (RMMS) which is being updated, to avoid a repeat of the serious damage to roads after record rainfall during the winter.
'Drainage is a major factor in road pavement design, ' he said.
'If drains are blocked or damaged and groundwater builds up in the subsoil, you can get a rapid deterioration in the road base.'
The problem was particularly bad for low lying cuttings, he said.
Excess groundwater softens the ground and reduces the loading capability of the road. Heavy traffic then damages the surface.
Most highway inspection procedures do not look at the state of road drains. 'Most work is confined to cleaning gully pots, channels and ditches, ' said Henderson, 'but in my experience siltation and blockage from vegetation - even from tree roots growing through drains - can cause major problems.' Pipe junctions are also vulnerable.
Damage could be detected early by making use of modern mobile inspection tools such as CCTV sledges and trolleys.
The Highways Agency confirmed this week that it was reviewing road drainage over the next year in its Trunk Road Maintenance Manual. It is understood that changes could include a less prescriptive approach to road drainage.