Motorcycles can ride along the 91 Toll Road for free. Here's the quote from the 91 Express Lane website...
Effective May 19, 2003, when you travel on the 91 Express Lanes with 3 or more people in your vehicle, you can use the 3+ Lane and you will travel toll-free, except when traveling eastbound, Monday through Friday between the hours of 4:00 p.m. and 6:00 p.m. During that peak time, when traveling through the 3+ Carpool Lane you will receive a 50% discount on the posted toll. This policy also applies to individuals on a motorcycle.
Source: http://www.91expresslanes.com/generalinfo/commonquestions.asp#8
So to ride free, you have to pass through the "3+ Carpool Lane". The only time it's not free for motorcycles is when you're travelling east, Monday to Friday, between 4:00pm and 6:00pm.
There used to be a small sign stating “Motorcycles OK” for the 3+ lane as you were coming into them. I assume it’s still there.
I think I recall seeing that sign now, but I forgot all about that.
It's good enough for government work...
I just checked the web site and motorcycles need to have a FasTrac to enter the 91 lanes. Going through the 3+ reduces the fee but is not free. Motorcycles are charged the same as 2 axle vehicles.
Yeah, I think it use to be free but that changed.
-Larry