Many of the responses in this thread as far as Big Dig tunnels are right on the money. The engineering was largely sound, and the problems could have been easily predicted and mitigated (epoxy issue excepted). The problem was solely with oversight and maintenance, and was the direct result of giving oversight to the Turnpike Authority.
The Turnpike Authority was run by, staffed by, and overseen by political hacks. This was caused by two main issues made inevitable by its governance structure.
The first was a lack of state oversight. The "independent" governance structure created a fiefdom of political appointees with insufficient political accountability. This led to it becoming a patronage dumping ground with underqualified, corrupt, and/or incompetent managers and employees.
The second issue was a lack of federal oversight. State Highway Departments have strict, strong oversight and project management from the Federal Highway Administration. Federal legislation is designed to govern State DOTs/Highway Departments - one per state - which regulate road and highway construction in the state. Independent toll authorities basically fall into a strange loophole of insufficient federal authority (and, probably, a lack of desire on the part of FHWA) to oversee them, and they are exempt from a lot of rules.
Note for example the "Citizens Bank Fast Lane"/EZ Pass change once the Turnpike Authority was eliminated. That was a safety issue. Corporate sponsorship is prohibited from highway signs ("Adopt a Highway" signs excepted). It creates confusion among drivers ("does my EZ Pass work here?") which causes accidents.
You may also remember years ago that the Pike used yellow speed limit signs at toll booths, which are advisory and not enforceable. When the media inquired, it had to be referred to the Pike Authority's General Counsel to research the issue. Any competent traffic engineer at a State DOT would know that, but no one at the Pike had a clue.
I have seen gasoline tankers in the tunnel before-- the rules are a joke and aren't enforced.
I have driven 80+ on every highway in MA inside 495 without so much as getting pulled over (I drove 25,000 miles a year) and often 85 isn't fast enough in the left lane of 495.
I agree on the gas tanker issue - that's bad and more enforcement is needed.
The speed issue however is a problem with the rules themselves, and a lack of public understanding of traffic engineering, not with enforcement.
Enforcement only affects average speeds literally during the time and place an officer is visible to a motorist and is conducting traffic enforcement. Speed limits don't affect average speeds at all, but, if set properly, can promote safety by decreasing speed differentials (people going fast slow down a bit, people going slow speed up a bit).
Speed limits are supposed to be set based on prevailing traffic speeds. Due to political reasons and simple inertia, major highways in Massachusetts have not been updated since the NMSL was repealed. The proper limit on Route 128 on the interstate-grade portions would be 70-75 if set properly. More rural roads such as 495 would be 80-85 or more.
The highway department has the authority to do this without legislative approval. Its engineers all know current highway limits are dangerous. Lots of their internal memorandums to higher-up officials basically say "I have no idea why we're posting the limit this low." It's just politics and inertia.
