I would be remiss to overlook Segesta having separately posted bus schedule information for Selinunte.
Most seasoned travellers will acknowledge that Segesta is one of the absolute glories of Sicily, to be ranked on a par (or nearly so) with Agrigento, Siracusa and Paestum. A half-day trip to Segesta is very highly recommended, even for the hurried tourist.
Fortunately, Segesta is even easier to reach by public transportation than Selinunte, since there is direct bus service from both Trapani and Palermo which allows tourists to see both the Greek Temple and the Greek Theatre without needing to rent a car or to take a much more expensive day tour.
The best connections are out of Trapani, daily and year-round. Tarantola Bus Lines has buses from Trapani's bus depot to Segesta at 8:00, 10:00 and 14:00, arriving 50 minutes and 39 kilometers later directly in front of the main gate of the Archeological Park. Return buses are at 13:10 and 16:10. I have taken this bus and can recommend it.
HINT: Take the 10:00 bus and return at 13:10 to allow sufficient time to see both the temple and the theatre. The afternoon combination cuts things a bit short.
There is also a bus service out of Palermo, although is not daily year-round. From April 1 through October 31, Tarantola Bus Lines departs from Palermo's Piazza Giulio Cesare (central train station) at 7:50 from Monday through Saturday, arriving at Segesta at 9:10. This bus also picks up in Piazza Politeama at 8:00. The return bus leaves Segesta at 11:50, arriving back in Palermo at 13:10. Distance travelled is about 85 kilometers.
NOTE: There is bus service also on Sundays from April 1 through October 31, but with different schedules which result in a six-hour layover at Segesta (too long for most people).
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