Long line for a cab at the airport? Cabs hard to catch on a rainy day? New car-on-demand services allow passengers to use their smartphones to order chauffer-driven Town Cars and comparable vehicles on short notice—in many cases, within just a few minutes. Among the smartphone car-on-demand services…

GroundLink is a network of independent black-car services in 400 cities worldwide. It usually can provide a car within an hour in those cities—within minutes in New York City. 877-227-7260, www.GroundLink.com.

Rate examples: Expect to pay perhaps $60 to $100 for a ride from an airport to downtown or vice versa in most markets, but Groundlink can be somewhat pricey for short rides within a city. “Ride now” rates in New York City start with a $10 base fare plus $4.60 per mile, with a minimum charge of $22.

Uber, which is owned in part by Amazon.com founder Jeff Bezos, serves fewer markets than GroundLink, but it often can provide a Town Car within minutes in such cities as Boston, Chicago, Los Angeles, New York City, San Diego, San Francisco, Seattle, Toronto and Washington, DC. Rates vary according to city, and a free app is needed. www.Uber.com

Rate example: In New York City, Uber’s base fare is $7, plus $3.90 per mile or 95 cents per minute for speeds below 11 miles per hour.

Taxi Magic allows passengers to use a free app on their smartphones to call for ordinary taxis. More than 85 cab companies in 45 large and mid-sized cities across the US currently participate. www.TaxiMagic.com