I am a traffic engineer in North Carolina and I have been setting speed limits for 7 years. In those 7 years, I have written over 800 speed limits for five counties.
My State is divided into 14 divisions and the traffic engineer in each division is granted by way of NC General Statute to investigate and determine what is the appropriate speed limit.
Speed limits are not easily determined for a roadway. Most people believe that if you lower the speed limit on a road that it will lower the actual speeds observed on that particular road. This is not the case. I have proven this time and time again with radar guns.
When we receive a request to lower ( and it is almost always a request to lower) we investigate the location and determine lane widths, horizontal and verticle curvature, pavement condition, clear roadside recovery area, location of high volume driveways (not private driveways to homes), crash analysis, and the biggest thing we record is the 85th percentile speed of traffic. This is the speed at which 85 percent of the vehicles are traveling at or below. You see constant enforcement can reduce observed speeds as much as 15 percent. You do not want to set a speed limit where everyone is observed going slower than and you don't want to set it too low where no one can observe it. Setting a speed limit too low breeds disregard for the speed limit signs.
Most people look at a speed limit and add five or ten miles to it and say I will not get pulled over if I go this much faster. When I set a speed limit I am telling people that if you go at or below this maximum speed then you should have the appropriate sight distance required for you to recognize a potential problem and safely react to it.
I hope this has helped shed some light on your question.
2007-07-25 12:24:35
·
answer #1
·
answered by traffic_joker 2
·
1⤊
0⤋
Most states determine speed limits by a couple of factors:
One of them is what type the road is: a private alleyway or driveway may have a speed limit of 15 MPH as they are narrow and sometimes unpaved roads.
A residential side street is likely to have a 25MPH speed limit as there are lots of kids at play and a lot can happen.
Main roads that are 2 lanes on each side are usually 40 MPH as there is a lot of traffic but not enough danger to warrant a slower limit.
Rural county roads generally 45-55 MPH, as there is not a lot of traffic and little stopping and starting at intersections.
Urban Interstates are 55 MPH and Rural Interstates are 65 MPH.
2.) The second way is by the surrounding environment the road is in: If it is near a big shopping mall or plaza and there are a lot of traffic lights, a 30-35 MPH limit is the best bet. If there is a school on a road, there will usually be a slower limit during school hours. Roads with heavy traffic conditions may warrant a slow limit. Speed limits will usually be slower around curves, bends, hills, etc.
3.) Thirdly, traffic engineers study the history of certain roads where a lot of accidents occur or where traffic laws are frequently disobeyed.
4.) A lot of the times, especially on highways, the posted speed limit may be 5, 10, or even 15 miles under the designed speed for the highway. This is so that when drivers exceed the speed limit, they are still traveling at a rate of speed that is "Reasonable and prudent" for conditions. Also, that way they can ticket people for going way over the speed limit and take drivers off the road who are posing a hazard to our community.
2014-10-05 01:22:27
·
answer #2
·
answered by ? 1
·
0⤊
0⤋
1. The Federal Government sets some rules, in concert with President and Congress. This applies to all states that accept federal money for highways. I think Oklahoma is the only one that does not, so they do not have to abide by the federal rules.
2. Eons ago there used to be an Interstate Commerce Commission (ICC) that regulated the Interestate Highway System on behalf of the federal government. I think that is now handled by the Federal Highway Administration.
Except for Oklahoma, there are these rules on the maximum speed limits, and other criteria that the states have to adhere to.
3. The Governor and Legislature of each state pass rules, so long as they are in accordance with the federal rules. Only Oklahoma gets to ignore the federal highway rules.
4. Each state has a Department of Transportation. It sends highway engineers out to examine each road & determine what speeds make sense, such as where dangerous curves are dangerous enough to require a slow down.
This is the outfit that determines what speed limits should be.
5. The actual posting of the signs might be sub-contracted to some company that bids on the government work, in competition with other companies.
6. Cities incorporated within a state, or counties, may also have their own staff to address inside the city limits.
Just like the state's rules have to be consistent with federal (except for Oklahoma), the city or county rules have to be consistent with the state.
2007-07-25 21:44:37
·
answer #3
·
answered by Al Mac Wheel 7
·
0⤊
0⤋
My brother works for our state in that department. When an intersection needs a change, whether it is a traffic light, stop light, or lane change, his department comes out to investigate the situation. They decide if there is a need based on traffic as well as known accidents at that intersection. I know he goes all over the state and his office is in the capitol. When we see those black rubber markers going across the road, they are done by his office and they are used to determine how many vehicles pass over them through that intersection. They also determine speed limits based on the amount of traffic as well as accidents and also pedestrian traffic as well. I know that school districts, residential areas and also shopping areas determine speed limits too because they tell his office just how much traffice and pedistrians can be in that area. He works for the State Safety Commission as a Traffic Engineer. Speed limits are governed by each state but usaully they all follow the same criteria. Boulevard streets that have medians are usually 35 mph., school discticts are usually 25 mph, etc. but there are variations for them depending on the location. They also determine where off and on ramps will be put and also where new roads will be put. They have to come out and inspect the area for them and also inspect the work on them when they are completed.
2007-07-25 18:28:53
·
answer #4
·
answered by 'Sunnyside Up' 7
·
0⤊
0⤋
Each state HWY dept decide because the condition and the type of road are all local situation.
But the Federal government has had big push to up the top speed (on hwys). That's because they believe that faster cars mean more cars (and less $$ they have to spend on new interstates). They threatened to to withhold federal high way funds if the states didn't up to top speed limit to 65.
But in the end, it is still the decision of each state's hwy department.
Good Luck.
===
Don't forget to vote for the BEST ANSWER - please - whoever it may be.
FACT: You also get +3 points when you vote for BEST ANSWER
2007-07-25 16:37:50
·
answer #5
·
answered by Lover not a Fighter 7
·
0⤊
0⤋
Traffic engineers. They study traffic patterns, accident data, road hazards: curves/hills/rr tracks, etc. and determine what is safe for a given stretch of road. Some speed limits are legislated, like school zones, residential, and so forth.
2007-07-25 17:49:04
·
answer #6
·
answered by Scott H 7
·
0⤊
0⤋