Editor’s Note: Over the next few months, I’ll be publishing a series of posts on weekday afternoons about becoming a better traveler. This week we’re turning our attention to car rentals. By the way, if you see something I’ve missed in this post, please tell me in the comments .

Do you need a rental car?

It seems like a no-brainer, but it really isn’t. Any time you’re traveling somewhere and you’re not in your own car, you’ll need to ask: rent or not?

The right rental vehicle can get you to your destination quickly and can give you freedom of movement when you’re on vacation. But an unnecessary car can also add to the expense of a trip, not to mention insert a layer of worry that you can probably do without.

When to rent:

• When the only way to reach your destination is by car. That’s the main reason people rent vehicles in the United States — there’s just no other way to get there. Only 70 percent of large metropolitan residents live in neighborhoods with access to mass transit service of some kind, and if you’re visiting someone in the suburbs, you really have no choice.

• If you need the flexibility of having your own set of wheels. Bus and train schedules aren’t always convenient. So if you need to be somewhere at a specific time — and this is a special consideration if you’re traveling on weekends or holidays, when mass transit is on a reduced schedule — then you may want to go with a rental.

• If you need to transport more than just passengers. Even if you could get somewhere by bus or train, you may have a lot of luggage or other personal belongings to carry with you. Mass transit isn’t suited to passengers with two pieces of luggage, let alone a business traveler with a box of books or samples to give away at a convention.

When to skip a rental:

• When you could get there safely and conveniently by mass transit. You’ll save hundreds of dollars (and maybe the environment) by forfeiting a rental vehicle on your next trip. Besides, what better way to see a place that the way the locals do?

• When everyone else is driving on the left. A warning to anyone visiting a country where they drive on the left side of the road, including Australia, parts of Africa, India and the UK: You’re asking for trouble. One survey found that 1 in 10 car accidents in Ireland involved tourists, many of whom were driving on the other side of the road.

• If you’re under 25, and definitely if you’re under 21. Many car rental companies won’t rent to you if you’re under 25, and virtually all of them refuse to hand you the keys to a car if you’re younger than 21. The only exception is if you are renting the car for work, and you’re covered under your employer’s insurance policy. By the way, there is such a thing as too old. American car rental companies normally don’t have published age limits, but many European countries do (it’s usually around 70). Check before you rent overseas.

• If you’ve have several moving violations. Your drivers’ license will sometimes be checked against a Department of Motor Vehicles database when you rent. If you’re flagged, you might not be able to rent a car. A car rental company may also turn you down if you’ve damaged a rental car in the past and didn’t pay for the repairs.

• If you don’t have a credit card. Many car rental companies (but not all of them) will refuse to rent a car to you without a credit card. Credit cards allow the rental company to pre-authorize a certain amount for the rental, and allow for so-called “late” charges (billing you after you’ve returned the car) if you’ve dented the vehicle. Check with your car rental company before you rent with anything besides a major credit card.

• If the cost of the rental vehicle outweighs your need to explore an area. Renting a car can be expensive, and with high fuel prices, insurance costs and other extras, it can really add up. If you have some flexibility, and can take a bus or train, it might be worth planning an itinerary that keeps you off the road, and out of a pricey rental car.

• If you’re just planning to stay at the hotel, and there’s a free van service to the airport. This is a common oversight, and results in a rental car sitting idly in a hotel parking lot for a week — and potentially, incurring a parking fee or a valet charge.

The decision to rent a car isn’t always an easy one. Take some of these questions into account the next time you’re planning your ground transportation arrangements. You may find that you don’t need a rental car for your entire visit — or at all.

(Photo: The Busy Brain/Flickr)