Even after recent fare hikes, getting to Europe this summer will cost you less than staying there a week or two. That's why you need to plan carefully about how you want to travel in Europe once you get there. A reader's question puts the main options in perspective: "Am I better off buying a rail pass or renting a car?" As usual, the answer is a lot more complicated than the question. But I can easily identify the basics.

Let's look at costs for a couple, traveling together, for both a one-week and a two-week trip. Here's a basic first-cut estimate of what you'd pay, total, for two people, with a rental car at $300 a week, plus operating costs, or two three-country Eurail Selectpass Saver Passes:

Renting a car

Although rental rates vary by country and by city within a country, I've found you can rent a compact car for under $300 a week in most of the popular European countries, and for around $250 in a few (Germany, Italy, and the Netherlands, when I checked). These rates include tax but not any collision insurance, which I presume, as loyal visitors to SmarterTravel.com, you know to cover through your credit cards. I also figure the operating cost of a compact car to be about 20 cents a mile.

Virtually all European compact and larger rental cars now come with air-conditioning—you no longer have to pay extra. But you'll still pay a premium of $50 to $150 a week for an automatic transmission.

You can cut your rental costs by going down to an "economy" car class, but I don't recommend doing that. They're too small and underpowered for extended driving.

Rentals that originate at some airports incur heavy extra fees and charges. When you're checking rates, take a look at the breakdown of fees. If it shows some heavy airport charges, try the "downtown" rates for a possibly better deal.

Extras to figure: parking (city hotels and near major urban sightseeing centers); highway and bridge tolls.

Traveling by rail pass

Instead of paying by the size of the car and the miles you cover, as you do with a car, with a rail pass you pay by (1) the number of days of train travel you're allowed during a one- or two-month period, and (2) how much geography the pass covers. I used the three-country Eurail Selectpass Saver Pass (available in first class only) as a typical best buy for a couple; "saver" passes throughout Europe require that both of you travel together whenever you take a train.

You can cut rail pass costs by limiting the number of days on which you can travel. All Eurail Selectpasses provide a minimum of five days; some national passes require only three days, with extra days on a per-day basis.

Saver passes are a good deal for many couples. But if either of you wants to take some solo excursions, you'll have to buy the more expensive individual passes.

Extras to figure: Transport between rail stations and hotels and between rail stations and important visitor centers; seat reservation costs (not trivial on top trains).

The choice by dollars

In our table, the rental car beats the rail pass for the one-week, short mileage trip, and it effectively ties rail pass for the two-week, shorter mileage trip. Rail pass, on the other hand, does better for either longer mileage trip.

• In general, rental cars look good for (1) short-duration trips, (2) trips where you move around a lot but don't log a lot of miles, or (3) trips involving several different countries. The figures above are for a couple sharing a compact car; the cost per person for four people sharing a midsize car would be sharply lower. Conversely, a car is an extreme extravagance for a solo traveler.
• Rail passes look good for (1) trips that log a lot of miles, (2) extended duration trips with a relatively limited number of days of heavy train travel, or (3) solo travelers.