[T-hawk]

1. Speed limits are slow and people are impatient. 55 MPH on a highway feels quite pokey in clear conditions when 75 MPH is easily possible with no appreciable loss in safety. And 30 MPH on surface streets is positively crawling. They are designed low knowing that the average user will exceed them, similar to the MPAA's tax on blank recording media where the expectation of violating is built into the product.

2. Blending in with the crowd. If the speed limit is 55 but everybody is going 75, it is safer for you to drive at 75 in smooth traffic flow rather than go 55 and create waves of darting and merging traffic trying to go around you.

3. Speed limits are sometimes applied dishonestly in the name of safety, when the real goal is revenue generation from violators. Such a law is immoral and unjust - government abusing its monopoly cartel power - and breaking it represents civil disobedience. This is more what the ancestor posts are getting at.

[stinkytaco]

So, I'm not a traffic engineer, but I do work with several on different projects.

In the city, speed limits are not designed for revenue or assuming most people will exceed them. They are designed because that is the safest speed to drive. They assume several things here:

1. Non-ideal conditions with many traffic lights require slower speed limits.

2. Views are often blocked by building, landscaping etc.

3. There are many types of traffic that do not conform to our "car society" but are still legal users of roads. (bicycles, pedestrians, etc.)

The 55 MPH speed limit was also not a matter of safety, but of energy savings. That's a whole different issue, however.

You can think what you want, but I can assure you that speed limits inside cities are not some sort of conspiracy. It's far more likely that most people feel they are better drivers with quicker reaction times than they actually have.

EDIT: Quick elaboration. There's a saying in architecture, "You design a parking lot for a busy Saturday, not the day after Thanksgiving." Speed limits are a compromise. You likely can go faster often (though like I said, most people are not nearly as good drivers as they think they are), but you must consider the times when you cannot go faster when designing the road (night, rush hour, rain, etc.). Speed limits are designed to find a good compromise. Remember, if this were a conspiracy, you don't have to be speeding to get a ticket, you can be pulled over for "too fast for the conditions".

The thing to remember is that speed limits are not set by politicians, they are set by engineers.

[weel]

In the end they are set by politicians. Not for malicious reasons; politicians don't need to be malicious in order to make bad decisions, they have plenty of other reasons for that. In many parts of the US, surface road speed limits are quite reasonable, but freeway speed limits are ridiculously low.

You are correct, by the way, as far as I know, that the 55mph speed limit was originally an energy conservation thing. This was during the oil crisis of the 70s, when it was federally imposed. Ever since the federal mandate was lifted, speed limits have been creeping back up, but at very different rates in different states.

To give a comparison, in France freeway speed limits are roughly 80mph in dry weather and 70mph in rain (I say roughly because they are, of course, in metric.) In Belgium, and the Netherlands it's 75mph, although The Netherlands has introduced many variable speed limits (electronic signs based on congestion) and recently bumped it up to 80mph on certain rural stretches (rural by Dutch standards). Germany, of course, has no speed limits at all on many long-distance Autobahns (about 50% of the network), although in metropolitan areas, contrary to popular mythology in the US, they often do have speed limits, which go by the charmingly long-winded name of "Geschwindigkeitsbeschränkung," often shortened in colloquial speech to "Tempolimit." The de facto speed limit on the unrestricted Autobahns is 125mph, since that's the fastest unmodified German cars will go.

So did some technocratic bunch of engineers evaluate the conditions in each of these countries and decide that somehow some subtle difference of geography that Germans are capable of safely driving a full 65 mph faster than Hawaiians?

I doubt it.

May I also remind the reader that East Germany used to have a rigorously enforced 60mph limit that was rather promptly lifted after the reunification, which was by no means an event of particular relevance to traffic engineering.

[nitrogen]

Politics definitely does influence speed limits. Example 1: a freeway was planned for decades, and when construction was finally ready to start, environmentalists sued to halt construction. Several years later, part of the settlement was a 55MPH speed limit.

Example 2: a small town declares with pride that all streets controlled by the city finally have limits of 35MPH or slower, even though there are several roads capable of much higher speeds.

[greghinch]

I'll tell you what, try riding a motorcycle sometime. You'll gain a lot more appreciation of what it means for you and the people all around you to be moving at 55mph (let alone 70+) in 2 ton metal boxes, in relatively close proximity. I think the problem is not that speed limits are too slow, it's that modern cars are too comfortable, lulling you into a false sense of security.

[soup10]

The problem is that 'safe driving speed' is completely dependent on road conditions(weather, traffic, pavement quality, time of day, day of the week(lots of drunk drivers on weekend nights), traffic makeup, etc.). Metal boxes with seat belts and airbags are far safer than motorcycles, but it's not appropriate to go 80 when motorcycles are nearby.

[neutronicus]

Try cruise-controlling at 55, even when everybody else is going 75. You'll get 4/3 the fuel economy, and it's so much less stressful, dirty looks or no.