Renting a car abroad: don't get carried away

'Throw the keys through the open window of the kiosk. We'll pick up the car when we open later”: Those somewhat unorthodox drop-off instructions I once received from a Hertz manager in Croatia illustrate some of the differences American travelers may encounter when renting a car abroad.

It pays to familiarize yourself with local policies and protocols in advance. Here's what you need to know before accepting the keys.

You may need an international driver's license

If you have a US driver's license, an International Driver's License is officially required (along with your state-issued driver's license) in Australia, Austria, Bulgaria, Czech Republic, Estonia, Italy, Japan, Poland, Romania, Serbia, Slovenia, Slovakia, Spain and Thailand, although its use is not enforced everywhere. It's also a good idea to carry an IDP, a booklet – slightly larger than a passport – that translates a US driver's license into 10 languages, when renting a vehicle in a country whose language is not in Roman letters written.

An IDP costs $20, is valid for one year, and is issued to each applicant by a local AAA office (the only issuer in the United States authorized by the Department of State). You must apply for one in the country that issued your regular driver's license.

Well-known brands can be franchisees

Car rental brands known to Americans operate all over the world; these include Alamo, Avis, Hertz, National, Sixt and others. You can reserve a vehicle through a company's US website or through a rental aggregator such as Autoeurope.comto compare rates.

The overseas offices of U.S. companies may not always be owned by the parent company. The discussion boards on websites such as Tripadvisor There are many commentators who criticize the franchise operations of major chains for not providing the service they expect from an American company.

Franchise or not, disputes with a foreign branch should always be submitted to American customer service, according to Hertz and Autoeurope.

Check the minimum (and maximum) age requirements

The minimum age to rent a car varies by country country and company, and it is indicated on the website of each rental company. Most countries charge a young driver surcharge for renters under the age of 25. Some countries, such as France and Germany, allow (but do not require) companies to rent to 18-year-olds, but for most countries, 21 is the typical minimum rental age. .

At the other end of the spectrum, Hertz does not rent a car to anyone over the age of 79 in Northern Ireland; those between the ages of 75 and 79 must have a doctor's letter stating that they are in good health, as well as a letter from their insurance company stating that they have not been in an accident in the past five years.

Reduce costs with a stick shift

Cars with manual transmissions are still popular in many European countries, so if you have no problem driving one, select that option. Renting a car with an automatic transmission can typically cost 30 percent or more.

Check your credit card's rental insurance coverage

Many US-issued credit cards will cover damage to your international rental car if you are involved in an accident, as long as you charge the card for the full rental price. Some issuers also require that the same card be used to make the reservation for the insurance to be valid. That collision coverage is primary, unlike in the United States, where your personal auto insurance covers the costs, while your rental insurance reimburses any deductible. Even if your credit card covers damage to your rental car, you will be responsible for the cost of damage to another vehicle if the accident is deemed your fault.

Please note that standard rental insurance for American Express cardholders is not available in Australia, Italy and New Zealand, and other cards may have different restrictions.

Familiarize yourself with local driving and parking laws

Before you go, learn the rules of each country, including the meaning of various road signs and markings. For example, if you see other vehicles with their wheels on the sidewalk – which is common in European cities with narrow streets – that doesn't mean it's legal to do so.

Autoeurope.com has driving tips for dozens of countries, not all in Europe, and the Britain's Automobile Association lists traffic rules for six European countries. Remember that many places next to Britain drive on the left (including Japan, Australia, New Zealand, South Africa and numerous Caribbean islands). And if you get a ticket, don't ignore it. The rental company will ultimately collect from you, along with administration costs.

Seat belt laws are often strictly enforced, with a separate fine (sometimes issued on the spot) for each occupant not wearing one.

Finally, many European cities restrict driving in central or historic areas only for residents or for those driving low-emission vehicles. Entering these restricted traffic zones may result in heavy fines, plus an additional fee from your rental company. Look for signs and gates (often marked “ZTL” in Italy).

Know your fuels

Diesel engines are very common in other countries; Putting diesel in a gas engine or vice versa can cause serious – and expensive – injury.

Although fuel pumps are color coded to indicate what they dispense, these colors vary by country and region. Fuel requirements are listed on a sticker on the inside of the filling door.

In the United States, black indicates gasoline, while green indicates diesel. In Iceland and other European countries it is the opposite: green for petrol and black for diesel.