“2. They often don’t work in practice because toll revenues rarely meet their protections over time. Too many motorists are so averse to tolls that they modify their driving patterns to avoid them.”
I think part of the problem with revenue projections result from the fact that the people making those projections don’t really understand the politics behind tolling, particularly how new ‘revenue engines’ (a little toll road lingo, by the way) often become piggy banks for other causes.
So the tolls have to be higher, the traffic further drops, and the net result is that you have taken a perfectly good good highway partially out of service.
I still remember the attempt to put tolls on I-80 in Pennsylvania about 15 to 20 years ago. The system was all set to start as Congress had approved several ‘Demonstration Projects’ to show the country the wonders of tolling our Interstates. But Congress had one little clause: Revenue collected from the new tolls could ONLY be used for maintenance and upgrades of THOSE highways (i.e., actual ‘user pays’, in this case, rather than the usual middle class tax increase disguised as tolls).
Guess what, Pennsylvania WALKED AWAY from the plan once they found out that they would be held to that clause...just wasn’t worth the effort to them to set tolls so low because then they’d have to explain the sky-high tolling rates on the PA Turnpike...where most of its ‘revenue’ money is now diverted for non-Turnpike uses.
The real purpose of that tolling plan was to generate revenue from motorists who travel through the state and don't pay any fuel taxes.