But 'free' isn't always what it seems, as a recent ruling by the Advertising Standards Authority (ASA) has underlined. The ASA upheld a complaint against the Portuguese airline, TAP, for an advertisement that promised a return flight to Portugal, plus 'free' car hire, for pounds 99. In fact there was also a compulsory additional charge of pounds 56 for insurance, plus a delivery charge for the car - details of which weren't given.
In response, the airline argued that the small print of the advertisement had referred to the fact that there would be extra charges, but the ASA nevertheless ruled that the total cost should have been included in the advertisement.
In practice, the ruling about total cost has only been of limited help to travellers trying to find a good fly-drive deal. Although the ASA argues that all such promotions and advertisements should give details of 'anything that is likely to affect the consumer's decision', there are often lots of extras or differences between the cars on offer. These are technically optional, but any sensible hirer would want to take account of them, because they make such a big difference to the final price.
One bugbear in European countries, particularly in Spain, is the size of car you get for your money. Vehicles are usually listed in groups according to engine size and rental charge, the cheapest being Group A and the most expensive Group D or Group E. With some tour operators, a Group A car is listed as a Ford Fiesta with a 1.1-litre engine, but with others you will get only a Fiat 500 with half the capacity - not the kind of car anyone would choose for touring the Andalucian coast or the Sierra Nevada.
Car-hire deals in the United States can be even more of a problem, as Independent on Sunday readers Jackie Green and Roger Dewhurst discovered to their cost when they booked a holiday to Colorado. Arriving at the car-hire desk after their flight, they discovered that their 'free' deal had melted away into a bill for pounds 347. Several crucial extras, buried away in the small print, had still to be paid for - including airport tax, collision damage waiver insurance, a charge for an additional driver and an upgrade to a bigger car (essential because they wanted to drive up into the mountains).
Car hire in the US is often priced to include only minimal insurance cover.
Travellers would be unwise to drive off without taking out both a collision damage waiver (which covers damage to the car) and the so-called 'top-up' insurance, which gives increased cover for personal liability. This will add around pounds 13- pounds 15 per day to the cost of the car. The extra charges don't end there either: there will also be a state tax (around pounds 1.33 per day, or pounds 20 over a two-week holiday) plus other charges for additional drivers, child seats etc.
In Europe, meanwhile, a new development to look out for is the 'airport surcharge', which can add between pounds 5 and pounds 15 to the final bill.
Being underinsured is one thing, but you can also end up paying for insurance you don't need - if, like most travellers, you have taken out a travel insurance policy. Personal Accident Insurance (usually called PAI and costing around pounds 2 a day) and Personal Effects Coverage (PEC, at around pounds 1 a day) are often listed at the bottom of the car-hire contract. I was caught out a year or so ago when a smooth salesman in Florence put a cross by the dotted line on each of these options. I signed them all, and only realised what I'd committed myself to when my credit card bill came through a month or so later.
There is some good news, however. The rapid rise of car- hire brokers, such as Holiday Autos and Suncars, has led to much more competition and some very good deals (helped by a recent price war between Hertz and Holiday Autos).
Prices are usually inclusive, though you should always check this, and there may be room for individual bargaining - so it is worth phoning around to get different quotes.
The brokers, who will sell through travel agents and tour operators or directly to the public, work by negotiating the best deals with national companies in the country concerned. You might book with Holiday Autos and end up with a car supplied by Dollar, for instance.
Holiday Autos: 071-491 1111; Suncars: 0444 456446.Reuse content