Hard-working Brits are facing stretching budgets, due to the overpriced food on offer at service stations.
According to Which?, bottled water is commonly four times more expensive there than in a supermarket – and that a single 500ml bottle cost £1.89 at one station in England.
A selection of snacks was found to cost anything between £7.49 and £10.31.
The consumer group also said that fuel was consistently more expensive at a service station – with filling up costing an extra £7.15 in the worst case.
Richard Headland, editor at Which? Car magazine, said: “By all means stop at a motorway service station to use the toilets or have a break from driving, but remember they don’t always offer value for money.
“If you’re trying to save this summer, buy food and drinks from a supermarket in advance and fill up your car from your cheapest local fuel station before you leave home.”
The Which? survey was taken in the run-up to the May Bank Holiday, a traditional time for British families to hit the road as they travel to their destinations for a weekend break.
It was also made as the motorway service station celebrates its 50th anniversary.