[Firehed]

Why have speed limits at all then? I've heard anecdotes of professional drivers getting out of massive speeding tickets because they know how to handle a vehicle at that speed (and presumably had the good sense not to be driving way faster than traffic if there even was any) and its certainly possible to get a speeding ticket when traveling under the limit if conditions do not permit.

Seems to me that they should be treated as good-weather guidelines (legally; that's already more or less the case in practice), and focus on the people driving recklessly - weaving in and out of traffic, going 10mph+ faster than everyone else, tailgating, etc.

[Anechoic]

Why have speed limits at all then?

Technically speaking, some states don't, at least not hard limits. For example, in Massachusetts, on roadways under MassHighway (well, now known as the MassHighway division of MassDOT) jurisdiction, speeds are supposed to be "reasonable and proper" (MGL Chapter 90, Section 17). Exceedance of posted speed limits are "prima facie" evidence of speeding, but not conclusive evidence, so it's technically possible to exceed the posted speed limit but not break the law if you can demonstrate that your speed is "reasonable and proper" (of course if you're not a lawyer or someone willing to spend a lot of money, this argument is not likely to fly in front of a magistrate). The MassPike and MassDCR roads require strict adherence to posted limits.

There are several other states that use "reasonable and proper" similar to MA, but I'd have to look them up to give a list. For the other states, I suspect the absolute limits are in place for simplicity.

[shiftpgdn]

Texas is a "reasonable and prudent for the conditions" state but good luck getting that argument to fly in kangaroo traffic court.

[csense]

> professional drivers getting out of massive speeding tickets

That seems unlikely.

> Why have speed limits at all then?

To reduce the frequency and severity of crashes.

To give people a baseline for safe speed. If most people's usual driving speed is "10 mph over the limit," then the effective speed limit is simply N+10 mph, where N is the number on the signs.

> tailgating

It's easy to deal with this effectively on your own. If you're being tailgated, just take your foot off the gas until you're 10mph under the limit. The tailgater will pass you at the very first opportunity. It's magic!

[zevyoura]

> If you're being tailgated, just take your foot off the gas until you're 10mph under the limit.

This advice (slow down when tailgated) is also what's advised at MSF training courses for motorcycle licenses also. It sounds counter-intuitive, but in addition prompting the tailgater to pass it also gives you more space to maneuver if things get dicey.

[cema]

  If most people's usual driving speed is "10 mph over the limit," 
  then the effective speed limit is simply N+10 mph, 
  where N is the number on the signs.

A big "if". As I recall, when speed limits were raised on some of the highways in Maryland from 55 mph to 65 mph, the traffic kept going at 72 mph.

In a society where everybody drives, speeds are set not so much by some kind of a law but more by the natural course of human actions.

[mindcrime]

Yep, traffic is largely self-regulating. Most people know how fast it's safe to drive and do it anyway. The others don't care about the "speed limit". Net effect, the actual posted speed limit and associated laws and corrupt bureaucracy are totally useless.

And never mind that "speed limits" are reverse engineered from observations of the natural speed of traffic in a given area in the first place.[1]

[1]: http://www.ite.org/standards/speed_zoning.pdf

[InclinedPlane]

> > professional drivers getting out of massive speeding tickets

> That seems unlikely.

It happens sometimes. A co-worker of a friend of mine was speeding in excess of 100 mph in a dodge viper and was pulled over and charged with reckless driving. However, the driver had completed the dodge viper training school so the judge ruled for him, and the officer had neglected to add any additional charges such as speeding.

[Someone]

If he wasn't charged with speeding, that is _not_ "getting out of massive speeding tickets".

[mitchty]

Sadly sometimes tailgaters don't get off your ass if you slow down. I slowed down to 30 once on a 70mph stretch before one guy finally passed while flipping me the bird.

My new rule is to just floor it to get other cars in between me and them.

[dasil003]

Wow. To paraphrase Team America: that guy was an asshole and a pussy.

[mitchty]

To be fair its really uncommon, but it has stuck out quite a bit in my mind.

The amusing part to me was he turned left only about a mile up so there was no real reason to stay tailgating (no off ramps up and coming). Just to note that I wasn't being a dick about things either.

[quellhorst]

If taking your foot off the gas still doesn't work you can also squirt the vehicle behind you by cleaning your windshield.

[brazzy]

> Why have speed limits at all then?

Because speed kills, plain and simple. It reduces the time you have to react to any problem, increases your braking distance and increases the damage and lethality of any impact. The latter two are affected with the square of speed.

There are very, very good reasons to have a universal hard speed limit.

[mindcrime]

There are very, very good reasons to have a universal hard speed limit.

There are? Well then what are they?

[sjwright]

Lower speed deltas create the safest driving conditions.

[brazzy]

Re-read my comment.

[joelrunyon]

Why have speed limits at all then?

Some speed limits were passed to help limit energy consumption - http://en.wikipedia.org/wiki/National_Maximum_Speed_Law

[shitlord]

> Why have speed limits at all then?

Probably because not everyone (and especially teenagers) has "the good sense not to be driving way faster than traffic"

[YokoZar]

Then why not make that the crime, rather than speeding in and of itself?

[noarchy]

It probably wouldn't bring in as much money to the local coffers.