Some of the route is on-road. From McKeesport, there's a 5 mile Clairton Connector to the end of the Montour, and that's all on roads (mostly light traffic). Then about 6 miles of the 40 mile trip on the Montour Trail to Robinson is on roads (either nice share-the-road or slightly less nice bypasses around unfinished sections). (Well, 8 of 40, with a current detour.)
Most of the route is virtually flat, but on crushed limestone. It would take me 6-7 hours, but I'm slow. Figure maybe 3-4 hours if you can maintain 15 mph under those conditions.
The trail has some damage from flooding last month, but it's fairly localized, and all but one short bit was rideable as of last week.
See also this recent thread.
2013-08-06 17:42:40