Two East Bay bus systems are offering discounted, unlimited rides to youths this summer, part of a joint promotion between Tri Delta Transit and the Western Contra Costa Transit Authority (WestCAT).

The passes, which are in the form of a waterproof wristband, cost $50 and are available to anyone 17 or younger. They are good for three months of unlimited rides, from June 1 through Aug. 31, on both transit systems.

Tri Delta Transit runs buses in East Contra Costa County. WestCAT runs local buses in West Contra Costa County from Pinole northward, and Express buses between Hercules and the El Cerrito Del Norte BART station. The youth passes are not valid on WestCAT Lynx Transbay buses.

The two transit systems connect at the Martinez Amtrak Station, via the Tri Delta 200 route from Pittsburg/Bay Point BART and the WestCAT 30Z Martinez Link from the Hercules Transit Center.

The passes can be purchased at the Tri Delta administration office, 801 Wilbur Ave., Antioch, from 7 a.m. to 6 p.m. Monday through Thursday and 8 a.m. to 5 p.m. Friday; and at the WestCAT administration office, 601 Walter Ave., Pinole, from 7:30 a.m. to 6 p.m. Monday through Friday.

Transit officials say they hope the program will result in more young people riding the bus during the summer and discovering the ease of using public transit. The program is supported by 511 Contra Costa, Contra Costa Transportation Authority, and the Bay Area Air Quality Transportation Fund for Clean Air.

For more information about the promotion and about either transit agency and its routes and schedules, visit www.trideltatransit.com or www.westcat.org, or call Tri Delta Transit at 925-754-4040 or WestCAT at 510-724-7993.

Contact Tom Lochner at 510-262-2760. Follow him at Twitter.com/tomlochner.