A few let you ride free and many offer discounts of 50 percent or more, but some make it difficult for visiting seniors. Again this year, I've examined senior transit policies for the U.S. cities most likely to attract visitors.

Unless noted, the minimum qualifying age for senior fares is 65 years. A Medicare card is usually accepted as ID, although you might also have to show a photo ID. Fares tabulated are for a single, one-way ride; many of these systems sell multi-ride, multi-day senior passes that are even better deals than a one-ride discount. Fare increases are pending in several cities. Senior fares may not apply to some special services such as "express buses" and transit to special events.

Stored value farecards are now often the only way to pay your fare, and some require special senior ID cards. Most buses require either some sort of farecard or exact change.

Pennsylvania is the most senior-friendly state for transit: Seniors now ride free at all times, with just Medicare ID.

•Philadelphia (www.septa.com, 215-580-7853); free on subway, light rail, bus; $1 on regional rail.

•Pittsburgh: (www.portauthority.org, 412-442-2000); free on subway, light rail, bus.

Some big U.S. cities make it easy for visiting seniors to ride on discounted fares: Just show ID at station or to vehicle driver, pay reduced cash fare.

•Baltimore (www.mtamaryland.com, 866-743-3682); 55 cents on subway, light rail, bus; half fare on regional rail.

•Cleveland (www.gcrta.org, 216-566-5100); 85 cents on rail, light rail, bus.

•Dallas (www.dart.org, 214-979-1111); 75 cents on light rail, bus, heavy rail to Ft. Worth.

•Denver (www.rtd-denver.com, 800-366-7433); $1 local, $2.25 regional on light rail, bus.

•Honolulu (www.thebus.org, 808-848-5555); $1 on bus.

•Minneapolis (www.metrotransit.org, 612-373-3333); 75 cents at non-rush hours on light rail, bus.

•Orlando-Central Florida (www.golynx.com, 407-841-5969); $1 on bus.

•Phoenix (www.valleymetro.org, 602-253-5000); 60 cents on light rail, bus.

•Portland (www.trimet.org, 503-238-7433); 95 cents on light rail, bus.

•Salt Lake City (www.utabus.com, 801-7434-3882); $1 on light rail, bus; $1.50 to $3 on regional heavy rail.

•San Diego (www.sdcommute.com, 619-233-3004); 50 cents. $2, depending on distance, on light rail, bus; minimum age 60.

•San Francisco (www.sfmta.com, 415-701-2311); 50 cents on light rail, bus; 62.5 percent discount on BART regional rail; 50 percent discount on CalTrain regional rail.

•San Jose/Silicon Valley (www.vta.org, 408-321-2100); 75 cents on light rail, bus.

Several other cities require that visiting seniors buy special ID or tickets, issued on the spot at a few offices during limited business hours.

•Atlanta (www.itsmarta.com, 404-848-5112); half fare on rail, bus.

•Boston (www.mbta.com, 617-222-3200); 50 cents on bus, 60 cents on subway and light rail, half fare on regional rail.

•New Orleans (www.norta.com, 504-827-7970); 40 cents on light rail, bus.

•New York City (www.mta.info, 718-330-3322); $1 on subway, bus; varying discounts on regional heavy rail.

•Seattle (http://metro.kingcounty.gov, 206-553-3060); half fare on bus, light rail, regional rail.

Finally, some cities deny the discounts to visiting seniors and instead limit senior transit deals to local residents. Unfortunately, Miami and St. Louis switched from all-seniors to local-only-seniors policy since last year's report, joining Chicago, Las Vegas, Los Angeles, and Washington in being unfriendly to visitors.

•CANADA: Of the important Canadian visitor centers, only Vancouver's transit system (light rail, bus) provides senior discounts that are easily available to visitors from the United States; Medicare card is accepted as senior ID.

(The preceding article by Ed Perkins was published June 1, 2009, by The Baltimore Sun.)