Rent it or cab it?
People like the freedom of having their own vehicle to drive about in, at home or when they travel, and the tendency is to book a rental car when you are away. But freedom comes with a price and it depends where your travel destination is as to whether you're best to rent a car or take a taxi.
Cheap ground transportation depends upon location, accessibility and extraneous expense factors, like gasoline costs and parking fees. Add to that the potential complexity of finding your way around a strange city, especially a large one, and you might change your mind about what freedom means.
A trip to, for example, New York City or Montreal, two North American cities with decent public transit systems, plenty of cabs, walkable areas in their cores, and very high parking fees, and you'll realize that a taxi will almost inevitably surface as the cheapest mode of getting around.
But what if you want a day trip to the Laurentian Mountains or the antiques stores of Hudson? That's the day to rent a car, or to find out if there is a luxury coach service to those destinations that returns the same day.
Car rentals are convenient, to be sure, but the costs add up quickly (don't forget insurance and occasional peak-season added fees), unless your airline points cover all or most of the cost; even then, in large cities gasoline and parking is very costly, and that is not usually included in credit card or airline rewards perquisites.
When does a rental car make sense? If you live in North America (and can't drive across the Atlantic Ocean!) And are vacationing in Italy, for example, landing in Rome and taking a motorcar tour of Tuscany and other regions from there, your only other viable option is the train. Like anywhere else, gasoline in Europe is expensive, but you can't take a full driving holiday in a taxi. But don't forget, there are guided tours and some taxi drivers will gladly spend a day with you, exploring San Gimignano; They are often the best tour guides, full of information about their homeland. And driving in other countries can be a harrowing experience, especially if it involves driving on the opposite side of the road than you are accustomed to!
Plan your itinerary, do an accurate cost comparison and decide whether a taxi or car rental, or combination of the two, is the cheapest way to get around when you reach your destination. And don't forget to ensure that your driver's license is current, and if you need to, get an international license before you set off for your trip. Happy motoring!