By on October 26, 2009

Cleared for take-off. As if. (courtesy

The Utah Department of Transportation (UDOT) announced last week that the experimental increase in the state’s maximum speed limit to 80 MPH has been a success in terms of safety. UDOT Deputy Director Carlos Braceras testified before the state Interim Committee on Transportation that that there has been no increase in accidents as a result of the higher number printed on the speed limit signs on certain stretches of Interstate 15. In 2008, the state legislature granted UDOT permission to test higher limits on rural sections of the road. Using crash histories, engineering studies, UDOT carefully selected the areas that it believed would best handle the increased limit. The department then conducted before and after surveys of speeds and traffic volume on the three sections where the limit was changed. Although the signs permitted another 5 MPH in speed, the results showed that drivers did not ‘take advantage’ of the new limit to drive significantly faster.

“Overall we saw speeds increase between two and three miles per hour,” Braceras explained. “The speed differentials did increase… We saw no change in accident history, which with how careful we were in choosing this location it wasn’t surprising to us, but it was very good news to see that… The number of vehicles exceeding the speed limit decreased 20 percent.”

With the speed limit posted at 75 MPH, 85th percentile speeds measured between 81 and 85 MPH — barely different from the 83 to 85 MPH speeds under the higher 80 MPH limit. The 85th percentile speed represents the speed at which 85 percent of free-flowing traffic feels is the safest. Engineers have determined that the greatest safety can be achieved when speed limits match the 85th percentile speed. State Representative James Dunnigan (R-Taylorsville) championed the results as evidence that the law allowing a higher limit has been a success.

“One of the concerns when we presented this bill a couple of sessions ago was that people would increase speeds to 90 or 95 and there would be tremendous carnage on the road,” Dunnigan said. “So even though it has only been a year, that has not happened. And really all that’s happened is that people haven’t changed their speed much — a little bit — but they’re doing so legally… So by increasing the speed limit to 80, we just made them legal.”

National Motorists Association researcher John Carr reviewed the data and suggested that coverage of speed limit increases always includes dire predictions of increased carnage. He pointed to an accident on the 75 MPH portion of I-15 just after the limit was raised on a nearby stretch as an example of skewed perspectives on the issue.

“It could have been anywhere,” Carr wrote. “Inside the 80 MPH zone it would have been taken as proof that the speed limit increase was recklessly endangering drivers. In the 75 zone it was not taken as an indictment of the low speed limit. That is how people think about speed limits. Ignore what they don’t want to believe, panic over what they do want to believe.”

UDOT is pleased with the results and will continue to watch the performance of I-15 under the higher limits.

“We believe this warrants further examination in the long term,” Braceras said. “We take safety very seriously… This isn’t something we consider to be a trivial undertaking — just go up and change the speed limit sign… We may want to after we’ve had a chance to evaluate this a little longer and we feel that we have something with more statistical significance it may be appropriate at that time to expand it to other sections of other highways.”


Get the latest TTAC e-Newsletter!

38 Comments on “Utah DOT: No Downside to 80 MPH Speed Limit Increase...”

  • avatar

    Good for all involved, and congratulations to the people of Utah!

    It is so rare nowadays to read a piece of news like this which reads like a rational, fact and science-driven discussion among and between technicians and politicians.

  • avatar

    I think it’s time to move south, folks. This kind of reckless lawmaking won’t fly here in the northeast. Think of the children!

    I’ve been in this country for over 10 years, yet the differences between north and south never ceased to amaze me. I’m really thinking of moving to Arizona or Colorado now.

  • avatar

    Thank God and the Founders for federalism.

    When I was a kid in western Kansas, the speed limit was “reasonable and proper.” Some motorists thought 95 or 100 was reasonable and proper. It was up to a trooper to prove the contrary — and that might be difficult when a road is straight, level and empty, and approaching vehicles can be seen three miles away.

    When the Kansas Turnpike opened in the 50’s, the limit was 80. And in those days, cars had flabby tires and loosey-goosey suspensions. Safety engineering was pretty much limited to laminated glass. Yet the main cause of accidents was falling asleep at the wheel after two or three hours of a steady 80.

  • avatar
    Mr Carpenter

    I have visited Utah and was highly impressed with the state’s beauty and the government’s seemingly common-sense approach.

    Kudos to them for actually utilizing their brains and also a major point nobody’s yet mentioned.

    Putting unnumerable laws into effect simply is a means to ensure that virtually everyone is a criminal, thereby having the means to control them. (Of course, the powers that be who make all of the laws don’t think they have to obey them, do they? Look at any day’s headlines to see that I’m correct in this assessment…)

    It’s very refreshing to see the opposite happening occasionally. Wish it would happen more often.

  • avatar

    so shortly the official legal speed limit on some of utah’s highways will be the same as the average speed of I-95 through philadelphia. wow.

  • avatar

    Let’s just change all speed limit signs to “Reasonable and Proper” and be done with it.


  • avatar

    Good for Utah.

    Similar to 50merc’s comment, I remember as a kid when virtually all of the Interstates in Texas had a 75 mph limit, with 65 mph at night(they had a unique dual speed limit sign; the lower part with the “65 night” was on a black background). The feds should never have been allowed to dictate speed limits (or any other clear state power) by withholding highway (or any other federal) funding.

  • avatar

    People, there is a simple explanation for these results. By law, the interstate highway system is designed and built to be used comfortably at 75mph by a person of average ability. That is why people don’t drive 55…. it is too slow. And why jacking the speed limit above 75 doesn’t increase the average speed…. the road is built to feel comfortable at 75. Sure, a few people will drive faster than 75 for short distances but those people are statistically rare. As long as the highway design standards remain 75mph then the average speed will hover around 75 no matter what the speed limit.

  • avatar

    In Italy, they raised the limit on some stretches of Autostrada from 130 to 150 km/h several years ago and the number of accidents and deaths decreased.

    It basically made the Caribinieri concentrate on other forms of risky driving behaviour that aren’t as easily detectable as speed.

  • avatar

    One of the things that’s always bothered me about speed limits is this: “Reasonable and proper” in a BMW 335i or Corvette is a lot faster than reasonable and proper in a Caprice, Dodge Dakota, or 95% of cars built before, say, 1995. Many of the newer and higher performing cars have additional handling, braking, run-flat tires, stability control, and crashworthiness that allows for higher-than-posted speeds with equal or greater safety than old heaps going the speed limit. Yet, the 1985 panel van has the same max allowable speed as my BMW. Very arbitrarty, for the sole purpose of easier enforcement. Reasonable and proper should be the speed limit, and the officer should have at least some leeway to give the cars that can handle those speeds a break.

  • avatar

    80 MPH really means 90 on cruise control will not get you a ticket.

    I drove cross country in 03, and in places like SD, I was going 80-85 on cruise but the highway quality sucked big time, full of potholes etc in places.

    One day of the three it took me from DC to Seattle, I covered 940 miles, with strictly two-digit speeds, and I was driving the old 1990 accord 5-speed coupe.

  • avatar

    carve :
    October 26th, 2009 at 10:59 am

    “One of the things that’s always bothered me about speed limits is this: “Reasonable and proper” in a BMW 335i or Corvette is a lot faster than reasonable and proper in a Caprice, Dodge Dakota, or 95% of cars built before, say, 1995.”

    Similarly, R&P in a recent 911 or a recent Ferrari is a lot faster than in the 335.

    And why stop there? R&P in broad daylight is quite different than at night, esp with limited visibility.

    Also, reasonable and proper for a race car driver is quite different than that for an 95 yr old lady with Alzheimers.

    I took my car home after my flight back on Fri at 7:30 PM and there was heavy rain. Everybody was doing 5 and 10 MPH at places, the 30 mile, 30 min drive back home became a 1-hr ride.

  • avatar

    I cannot think of a rural Interstate in our country that one cannot safely travel on at 80 MPH or more. Urban areas, of course, are a different matter.

    Kudos to Utah for doing the obvious and smart thing.

  • avatar

    Kudos to Utah. Intelligent highway administration is nice to see.

    @texlovera: We used to have those dual signs in Saskatchewan, too. They were removed when we converted to metric in the late 1970s. The speed limit on better roads was “Maximum 65” (similar to today’s signs) and below that was a white-on-black sign that said, in the same format, “Night 60”. Conversion to metric changed them to a single, more psychologically pleasing (if compromised) “Maximum 100” (which is now 110). We would probably have a higher speed limit if the authorities weren’t worried about people with modest sedans and pickups and well-worn all-season tires thinking that it was safe to do 120 km/h on a slippery January highway.

  • avatar

    Wow. A Delta hub, the Jazz, polygyny and now speeding — Utah’s got it all.

  • avatar

    80 mph in Utah? That’s nothing. Their roads are smooth. Here in Michigan, we drive 80 mph in 70 mph zones with roads crumbling under one’s tires. High times.

  • avatar

    My first thought was: There are speed limits in Utah? Having never driven on the highways in the state at less that 85 – and often in 3 digits – (usually on my bike), and never seeing HP except at accident sites, I just figured the speed limit signs were merely advisory. I love that, now if we could get the Washington State patrol not to be such an extension of the state tax system, life could actually be ok. Well, anyway, kudos to Utah.

  • avatar

    mtypex: “80 mph in Utah? That’s nothing. Their roads are smooth. Here in Michigan, we drive 80 mph in 70 mph zones with roads crumbling under one’s tires. High times.”

    Ultimately, it is much smoother at higher speeds because you fly over most of the potholes. However the ones big enough to fall into and hit will make you think otherwise.

  • avatar

    As much as I would personally appreciate the change to ‘Reasonable and Prudent’ as the speed limit, I think it would cause accident rates to rise steeply. I’ve always believed that ‘speed kills’ was a stupid saying, but that its first cousin ‘variable speeds kill’ was quite accurate. Having vehicles on a highway going anywhere from 50 to 150mph at the same time adds another level of complexity for drivers to manage, and not everyone will be successful…

  • avatar

    “so shortly the official legal speed limit on some of utah’s highways will be the same as the average speed of I-95 through philadelphia. wow.”

    Yes, but the limit on I-95 in Philadelphia is 55. The man can pull over anyone and stick ’em with a ticket. If you are lucky they will write it as a less severe violation. I see lots of accidents due to people seeing a police vehicle in the median and trying to stop from 85 to 50 quickly.

  • avatar

    Back when I lived in Colorado, when some roads went to 75 mph, I recall later reading that increasing the speed limit actually helped to improve traffic flow and lower accident rates as more of it was flowing at a closer speed. In fact increase in speed limits did not bring about the death of more children as was claimed by some.

    But now in the Midwest, IMHO, the speed limit is kept low for the benefit of ticket revenue. What wouldn’t be a ticket for going 5 mph over is now a ticket for going 15 mph over!

  • avatar

    This is good news. I’d be lying if I said I was not surprised. I’m guessing that some people in Washington are really angered by this display of common sense and independence, and could be planning some kind of retribution. Might be time for the state to consider cessation. I thought people in Utah were all nutballs. Goes to show how wrong you can be.

  • avatar

    mtypex: I couldn’t believe that people would go so fast on Michigan ‘highways’ (if that’s what you can call those broken up strips of pavement). I think that might have been the 2nd scariest driving I’ve ever done (after PA turnpike in a platoon of trucks in the mountains about 1 month after getting my license).

    About ‘Reasonable and Prudent’, remember that it’s also conditional on what other people are doing around you. So you might be in a ‘Vette or M3, but it wouldn’t be called R&P do be doing 110 while everyone else on the road is doing 75-85.

  • avatar


    PA also has some of the worst roads I’ve ever seen. Crossing the state line from Delaware or Maryland, the roads quite literally turn to crap just as soon as you cross the state line.

  • avatar

    Man Utah is so dumb. Why would they do that when they can lower the limits to 55 (for safety and the earth btw) and set up photo radar cameras??


  • avatar

    You know what would be really cool: Adjustable speed limit signs. Maybe on an 85 degree blue-sky day on a freshly paved straight road in Arizona, the limit could be adjusted to 100 mph (I’ve actually traveled in AZ in traffic conditions moving almost that speed in similar conditions). At night, it turns down. Animal-collision prone areas? Down. Lots of onramps, offramps? Down. precipitaion? Down. It should be adjustable downwards that the speed LIMIT could be as low as, say, 20 mph during a deluge or night-time snow storm. Speed limits up-hill would be higher than speed limits downhill, since you need less braking distance going up hill.

    You know what would be even cooler though? Wireless speed limit signs mounted ON THE DASHBOARD. You buy one for $25 when your car is registered, and a little solar panel keeps it charged. Now, speed limit could also be adjusted based on things like braking distance of your car, your tires (if you have summer tires, higher limit in the summer, lower in the winter & vice versa for winter tires), and ideally, you could get higher and higher skill-level ratings on your license to increase the limit. Talk about motivation for better driver training! Your in-car speed limit would drop as you approached traffic moving much slower. Of course, there’d be limits to this (only implemented on high-traffic highways, low traffic where speed differential is less a concer, etc.)

    Ideally, the speed limit wouldn’t be any lower than what you see today on the signs except in very bad weather or if you drive a shitbox.

  • avatar

    I drove this piece of highway going to my niece’s wedding in Salt Lake this past June.

    That “test area” was nice, road surface smooth, a treat to drive it @ 80 without fear of being pulled over because of out of state plates and breaking the speed limit.

  • avatar

    @alex_rashev, keep your kids off the road then, that’s no where to let them play, you’re a horrible parent! hehe. I think of your kids everytime I pay state tax, don’t you worry. Now reward me with something back, it’s a two-way street/interstate, ya know.

  • avatar

    carve :
    October 26th, 2009 at 4:31 pm

    You know what would be really cool: Adjustable speed limit signs. Maybe on an 85 degree blue-sky day on a freshly paved straight road in Arizona, the limit could be adjusted to 100 mph

    See Germany.

    I think the next toy in ultra-lux cars is something you posted – there are now cameras that can read the speed limit sign and display it on your nav/dashboard.

    The issue of that in the US (and this was true in Ohio until a couple of months ago when the state went to a uniform truck/car speed limit) is some states use dual speed limit signs or signs like the NJ Turnpike uses with neon or other variable display signs.

    Last but not least, places like Germany and Italy have done studies about what speed most people feel comfortable driving at. I believe Germany concluded around 85mph is the average comfortable speed limit.

    Of course their driving laws are far more rigid than ours and I swear I’m about ready to bump-draft the next (***)hole that is driving 56 in the left lane in a 65 zone. Can’t we start ripping driver’s license away for that junk??? That causes more accidents and road rage than anything else out there (besides drunk/buzzed driving.)

  • avatar

    Now that’s a law I can live with. Good job, Utah!

    I believe Texas also has some 80 mph interstate.

  • avatar
    Björn Abelsson

    Obviously most of you making comments here do not know the elementary basics of physics. Speed energy increases much faster than speed, and the risk to get killed in an accident increases even faster. If the average speed increases 2-3 miles per hour the risk to get killed increases 10-15 %. This is not belief. This is science.

    Probably this lack of understanding is one of the main reasons why the death rate on US motorways is 2.8 times higher than in Sweden and 1.9 times higher than in Germany.

    Björn Abelsson
    Transportation planner, Sweden

  • avatar

    Bjorn, the severity of accidents and the possibility of death in any highway crash is something that all Americans know from before they start driving.

    However, we make the cost-benefit analysis as individuals to drive at these speeds in order to save time on the comparatively long drives in the US. There is in almost every case an alternative road to use for those who do not wish to take the risk of driving at a higher rate of highway speed.

  • avatar
    Björn Abelsson

    A cost-benefit analysis of highway speed shows clearly that speeds over about 60 mph (=100 km/h) are expensive. The benefits (shorter travel time) do not balance the costs (accidents, petrol consumption, noise, pollution, road maintenance and congestion).

    And obviously highways (roads with dual carrigeways where the two directions are safely separated)are safer even at 80 mph than a two-lane road with traffic in both directions at a much lower speed (at least down to 40 mph).

    But do Americans value time so much more than life, compared to Europeans?

    Björn Abelsson
    Transportation planner, Sweden

  • avatar

    But do Americans value time so much more than life, compared to Europeans?

    Given that fatality rates are higher in numerous European countries than in the US, as we might say here, that dog don’t (sic) hunt.

    If the average speed increases 2-3 miles per hour the risk to get killed increases 10-15 %. This is not belief. This is science.

    It is belief. Do a correlation study of safety and speed limits, and you won’t find the correlation.

    The Netherlands have a lower motorway fatality rate than Sweden, even though it has a higher speed limit (120 km/h vs. 110 km/h). Ditto for the UK, even though the 70 mph limit is basically unenforced below the 80 mph level.

    It’s simplistic to believe that higher limits lead to crashes, given that (a) speed limits don’t necessarily impact actual travel speeds and (b) the aforementioned lack of correlation.

    If you are a transport planner, then surely you must be familiar with the 85th percentile concept and the failure of speed limit reductions in substantially reducing travel speeds. The fact is that most drivers drive at the speeds that they find comfortable, and the sign doesn’t influence their behavior unless they believe that they could be caught. Since reducing the limit doesn’t slow drivers down, it is difficult to claim that changing the digits on a sign will provide a benefit to anyone.

  • avatar

    Bjorn, how is petrol consumption, noise, pollution and road maintenance affected by increases in speed limits within the 55-90 mph (100-150km/h) range on divided multilane highways?

    Accident rates are obviously controversial, and I can’t imagine higher speeds increase congestion, but what about those others?

  • avatar
    Björn Abelsson

    Well, I guess we know more about which dogs that hunt and which that don’t here in Northern Sweden, where hunting with loose dogs is a very serious matter for a lot of people, than you do in Southern USA. Not that I hunt myself, and not that hunters even in Sweden seem to care much about traffic safety . . .

    But: not very many European countries have death tolls on their roads that are as bad as the average US death rate. There are a few, like Slovenia, the Czech Republic and (surprisingly!) Belgium. But countries like France, Austria, Denmark, Finland, Spain and Italy rate better than US (for some of these countries I have not found the rate per vehicle-kilometre, but used the rate per capita instead, which may be unfair for US with many cars per capita). And actually the Netherlands has a higher death rate on motorways (2.1) than Sweden (1.8).

    There are very many correlation studies made on speed limits, actual average speeds and accidents. A presentation of those studies can be found at The overall result of all these studies is that a 5 % increase in average speed will lead to a 25 % increase in death accidents.

    Pch101 has a point, though, that it is the real speed that matters, not what the sign tells. But reducing speed limits actually does slow drivers down, as well as increasing those leads to increased speed on the road. The current example from Utah is rather typical. An increase of the speed limit with 5 mph means that the average speed on the road increases 2-3 mph. Of course the correlation between signed speed and average speed depends a lot on enforcement. With proper enforcement, e.g. speed cameras, very few drivers will drive faster than they are allowed to. Without enforcement, I can agree that “changing the digits on a sign will [not] provide a benefit to anyone”.

    Björn Abelsson
    Transportation planner, Sweden

  • avatar
    Björn Abelsson

    At high speed most of the engine power is required to overcome the wind drag. And that grows with speed at the power of 2. This means, that if the speed increases from 100 to 150 km/h the wind drag increases with a factor 2.25. Petrol consumption does not increase quite as much, but with about 60 %.

    Pollution increases about as much as fuel consumption, while noise increases with the logarithm of the speed that is not as much as the speed. Road maintenance depends a lot on vehicles and tyres. If the proportion of heavy vehicles is big, speed does not affect road maintenance that much. But where there are mainly cars and especially if they have studded tyres the wear on the road is much higher at higher speed.

    The capacity per lane is highest at 30 km/h (1630 veh/hour). At 100 km/h it is 1122 veh/hour and at 150 km/h it is 865 veh/hour. This is the theoretical capacity if all drivers respect the need to be able to stop if the vehicle ahead suddenly stops (1 sec reaction time plus braking distance). In practice many drive closer than that, which is why rear-end collisions are common at high traffic flow.

    Björn Abelsson
    Transportation planner, Sweden

Read all comments

Back to TopLeave a Reply

You must be logged in to post a comment.

Recent Comments

  • Inside Looking Out: There is the easy solution – spin-off Polestar as a new company with profitable assets and...
  • el scotto: Can I use the word “Amazonized”? One of the big car companies will look at Carvana or another...
  • Add Lightness: Good to see the electric motor power and battery pack capacity stated with the correct units. Any idea...
  • Inside Looking Out: “like Bugatti and Maybach did.” In the end all these zombies get brought up in...
  • Add Lightness: Jaguar will not go extinct, it will just have a long, long hibernation like Bugatti and Maybach did.

New Car Research

Get a Free Dealer Quote

Who We Are

  • Adam Tonge
  • Bozi Tatarevic
  • Corey Lewis
  • Mark Baruth
  • Ronnie Schreiber