No train service reaches Niagara on the Lake and the town has a limited bus service. So if you're interested in visiting Niagara on the Lake but don't have access to a car, you can take a bus or train into Niagara Falls, and then proceed by cab or shuttle to Niagara on the Lake. Here's contact info on several cab/shuttle companies:

The cost for a cab ride to go from Niagara Falls to NOTL, or vice versa, would be approximately $35 CAD, one way. 

For Niagara on the Lake bus routes, visit www.notl.org.

During the summer months, the Niagara Parks Commission operates a shuttle as an extension of the WEGO system, from the last 2 WEGO stops (Floral Clock and Queenston Heights Park) to Fort George in Old Town. Price is $5 each way and is not included in the standard WEGO day pass. http://www.niagaraparks.com/files/NOT...

Another option for getting around while you're in Niagara on the Lake is the electric bike rental company, eSkoot Niagara: www.eskoot.com