Highways firms led by Colas said their employees are increasingly being attacked verbally – and by  missiles hurled by drivers frustrated by delays.

Colas is now calling for different speed limits near highways sites.

“Unusual” speed limits like 9.5 mph would grab drivers’ attention and slow them down to the point where they can see the road workers which could prevent them from abusing civil engineers.

Dennis Gregg, who leads Colas’s traffic management team, said: “Our employees have reported numerous incidents of being at the end of abusive language and, worse, being struck by empty drink cans, apple cores and stale sandwiches.”

One of his company’s employees was struck in the face by a full pot of family size yoghurt.

Gregg said: “Luckily he escaped any serious injury. But such wanton misbehaviour could easily harm someone permanently.”

Truck drivers are the worst offenders followed by taxi drivers who ignore warning signs and diversion cones – and sometimes even barge through at high speed on lanes where work is going on.

Rubbish throwing happens mainly through the night and at weekends and seldom involves private motorists.

Gregg said: “We appreciate that drivers of heavy goods vehicles have strict journey schedules to meet and probably get frustrated. But they don’t seem to appreciate that we are working to ensure their future safety.”

Colas has now wants the Civil Engineering Contractors Association to ask the Highways Agency and local authorities to try lowering the limits to strikingly odd levels to see if it improves drivers’ behaviour.

Alasdair Reisner, CECA’s director of external affairs, said: “Sadly, abuse at road works is all too common, both on local and strategic roads.

“The Highways Agency has been working to combat the problem with media campaigns. We are keen to work with others in the roads sector to change the public’s views on safety at road works.”