FAMILIES who take to the road on days out during the holidays can save enough money through simple fuel-saving driving techniques to round off the summer with a free trip to the cinema or for a lunch out, according to the AA.

On the motorway alone, as much as £20 to £25 can be clawed back from day trips to the seaside, amusement parks or visiting relatives. Even motorists taking friends and family to airports can recover the cost of short-term parking from a round-trip of 80 miles.

Ways of burning money on the motorway include:

l Driving with under-inflated tyres, with the window or sun-roof open or the air conditioning on and carrying an extra load. Combined, these factors can sap fuel at the rate of 45 pence per 50 miles of motorway in a small car and 43 pence in a medium car.

l Going with the flow at 80-85 mph instead of the 70 mph national speed limit. For every 10 miles, fuel costs for a small car go up 32 pence and 29 pence for a medium saloon.

l Standing still in a traffic jam. A small car idling in a tailback squanders fuel at a rate of one penny every minute while a medium-sized car loses two pence every minute.

l Driving with an empty roof rack. This destroys a car's aerodynamics, boosting fuel consumption by a staggering 10 per cent or more at motorway speeds. This adds 47 pence for every 50 miles for a small car and 60 pence for a medium car. Fully loaded, the penalty can rise to 30 per cent depending on the luggage height.

AA head of technical policy, John Stubbs, said: "With petrol priced at £3.36 per gallon, lumping together the savings from just two or three fuel economy driving techniques can reap a significant pay-back.

"People don't see themselves as 'gas guzzlers' but they may be surprised how much fuel and money they can save over the summer.

"In many respects, these fuel-thirsty factors are just the thin end of the wedge. Planning routes to avoid getting lost and driving unnecessary miles, checking traffic information before setting out, avoiding peak periods and filling up before getting on the motorway all rake back the petrol pounds, 76 per cent of which is tax."