Drivers are being urged to stop littering roads with fruit peel and apple cores to cut deadly wildlife collisions.
The organic matter can "lure animals" into the road where they are hit by vehicles, National Highways said.
A survey of 2,000 UK adults it commissioned found 45% did not think litter included biodegradable food.
A Surrey wildlife charity said an "unheard of" number of injured foxes needed treatment due to dropped litter.
National Highways has launched a campaign, supported by the RSPCA and Keep Britain Tidy, to encourage drivers to "lend a paw - bin your litter".
'Lethal roadside restaurants'
Nick Harris, National Highways chief executive, said littering was a "dreadful social problem".
He said: "It's not just unsightly, it can have a deadly impact on wildlife, turning verges into lethal roadside restaurants.
"We're working hard to tackle it on our roads, with our people litter-picking every day.
"To keep them safe we have to close motorway lanes, which delays drivers and costs millions of pounds."
The RSPCA said it has had more than 10,000 reports of animals found injured, trapped or dead from discarded litter in the last three years.
Simon Cowell, of Wildlife Aid Foundation near Leatherhead, told BBC Radio Surrey there had been 78 injured foxes brought in locally for treatment this year due to people dropping litter and animals getting trapped in fences.
He said: "It's just unheard of. We've never had so many before. Ninety-five per cent of cases we get now are because of man."
Helen Bingham, from the charity Keep Britain Tidy, told BBC Surrey: "We are killing a huge amount of wildlife by just mindlessly throwing stuff out of our cars, so the message is don't throw anything out of your car window."