Speed Trials
Reading this article about “intelligent speed adaptation” — or devices that limit speeds according to the posted speed of the road (imagine that!) — in Australia (where most of the ISA research is being conducted), I was curious about this phrase:
In cases of emergency there is an override system whereby the driver can either flick a switch or floor the accelerator to disable the safety device and put the car back in manual control.
The immediate question that springs to mind is how long can the device be disabled for? Would drivers not simply disable it for their entire trip? Is ISA meant to be a merely advisory technology, a bit of feedback to discourage speeding, or an actual enforcement mechanism? I tend to think the whole issue of hypothetical speeding for some emergency is a bit overblown (when compared to the potential safety benefits of ISA) — for something like crash avoidance, braking is typically just as valid a response. On the other hand, there are moments on Australian roads, as in the photo above, where a bit of speed might be desirable.
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This entry was posted on Tuesday, June 2nd, 2009 at 12:50 pm and is filed under Traffic safety. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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June 2nd, 2009 at 1:42 pm
The Road Warrior is one of my all-time favorite movies! But, seriously, I find when driving on the highway between Washington, DC and Pittsburgh, there are times when I DO have to speed up considerably to avoid being rear-ended by big rigs going down mountains. Much of the highway is two lanes in each direction [with a third lane added only in the uphill stretches for slow-moving vehicles], so there is no place to go but full steam ahead in some situations.
I could see people being lazy enough in ordinary traffic not to bother overriding the governor, because they’re too busy talking or texting on their phones, or whatever. [I mean, people are too lazy to use turn signals, and that takes the flick of a finger.]
June 2nd, 2009 at 3:23 pm
The real question is should there be a speed limit.
I can see value in the system in highly pedestrian dense areas. There, speed can actually be a factor in safety. Also, at those low speeds, it’s hard to imagine a need to go faster to avoid something. I bet this will just cause more congestion though.
June 2nd, 2009 at 3:29 pm
Nancy said: “there are times when I DO have to speed up considerably to avoid being rear-ended by big rigs going down mountains”
Really? Trucks don’t have brakes? Truck drivers can’t see traffic in front of them?
June 2nd, 2009 at 4:54 pm
having driven frequently in the mountains of the west, i have never, not once been in the situation where i needed to speed up to avoid being rear ended by a truck. truck drivers are usually skilled professionals who know how to control their rigs.
of course, on every major decline there are several “runaway truck pits” so these do happen rarely, i suppose.
June 2nd, 2009 at 6:32 pm
MikeOnBIke and Doug-
Generally I drive the speed limit or under, which is 60 or 65 on the roads I am talking about. Trucks coming down these mountains always go over the speed limit. I stay in the right lane unless I am passing someone. Yes, I do need to speed up to 70 MPH or so frequently to stay ahead of descending trucks and allow them enough time and space to pass me.
June 2nd, 2009 at 6:42 pm
Aaron, I agree that speeding is bad in pedestrian-heavy areas but I don’t think that going at a reasonably slow speed causes congestion. [If anything, it probably improves traffic flow because there are fewer accidents.] Speeding is also bad in less dense areas where pedestrians need to cross roads but are unable to because drivers are going 40 in a 30 or 25 MPH zone and can’t slow down or stop in time to allow peds to cross. This happens frequently on the road in front of my house. The speed limit is 30, it is next to a school, and there is a marked crosswalk mid-block. However, drivers habitually go well over the speed limit and only about 1 in 50 drivers ever stops for me when I’m trying to cross at the crosswalk, and I’m usually holding a big yellow umbrella.
Speed limits aren’t just about how one is able to handle the curves, it’s about the other users of the road. When motorists speed, they rob other users of their right to use the road in a safe and lawful manner.
June 2nd, 2009 at 6:52 pm
Having lived in Australia, and the nannyism that seems to be prevalent there, I would say the idea that the governor can be “turned off” is simply to appease people who may vocally oppose it. Then once it is implemented they will show that people who had it turned off were x times as likely to crash, and use that as the reason to ban speeding altogether.
The Aussies are a weird bunch on one had they have an obsession with V8’s and muscle cars. On another entirely is the green face the government tries to put on.
June 3rd, 2009 at 7:00 am
Nancy, I can’t comment on the cross walk issue. But that sounds like an area where there should be a speed limit. It also might be that your path doesn’t intersect the driver’s path and he shouldn’t be slowing (stopping shouldn’t ever be necessary) for you, you both should simply procede. Generally I make eye contact before proceding, as long as a driver acknowleges your presence and you move with determination, showing your intent, you should be safe.
As for congestion, whenever you lower the average speed you increase the amount of time a vehicle is on the roads and therefore the number of vehicles on the road at anytime. And, at especially at speeds below 35, you increase the fuel consumption per vehicle mile when you slow down (assuming the frequency of stops isn’t high).
Speeds slower than the posted speed are likely to increase the frequency of stops as well, further decreasing efficiecy in both time and fuel.
Ideally, I’d like to see electronic speed sign that if followed will coordinate flow with traffic lights and reduce (possibly even eliminate) the frequency coming to a full stop.
I’d also like to see an informational campaign to get people to get up to speed more quickly. It’s seems to that getting up to the appropriate cruising speed faster is more fuel efficient (provided that lights aren’t timed with the assumption that drivers will doddle at the green light. If you know that’s the case, you can cruise at a slightly lower speed or take your foot off the accelerator earlier to avoid the stop).
June 3rd, 2009 at 9:06 am
The kind of behavior I see in the DC metro area is this: drivers speed to get to the next red light. Between lights, they put everyone else in danger, and they don’t ease congestion because they spend the same total amount of time on the road. Revving up quickly isn’t energy efficient.
June 3rd, 2009 at 9:59 am
Actually it is, up ’til about 4000RPM (fuel consumption is lowest per power delivered at about 2100RPM, but it doesn’t increase significantly with additional power until much higher RPM). What’s inefficient is continuing to accelerate up to a stop. The drivers should be accelerating quickly, but laying off earlier.
June 3rd, 2009 at 10:33 am
Small amounts of power at low engine speeds actually consume more fuel than higher amounts of power and RPMs.
You may need to register to view the graph. Registration is free.
http://www.physicsforums.com/attachment.php?attachmentid=18980&d=1242755862
June 3rd, 2009 at 10:45 am
Okay, so I’m wrong about the efficiency, but I don’t think it’s safe, especially when you might run into a red light runner. I am also more concerned about people other than just motorists being able to use roads.
June 3rd, 2009 at 10:49 am
(it looks like I was wrong about 2100 being lowest fuel consumption. It looks more like 2500 for that engine– that’s for accelerating, not cruising)
June 3rd, 2009 at 10:54 am
That’s why I look first.
And I slow to a speed I can easily stop at for residential areas.
June 3rd, 2009 at 11:20 am
I’m glad to hear it, Aaron. I wish more drivers were like you.
June 3rd, 2009 at 2:33 pm
Here’s a neat paper: http://www.monash.edu.au/cemo/roadsafety/abstracts_and_papers/096/HawSym2.pdf
It suggests getting RPM up to 3000, but not higher, when accelerating. It also shows that traffic calming increases fuel consumption with questionable safety benefit.
But it does seem to indicate lower speeds are safer.
June 4th, 2009 at 7:19 am
I was considering the effect speed limiters would have here in Baltimore, what with the frequent drive-by shootings, robberies, and rival gangs chasing each other - all in areas with posted 15-20MPH speed limits.
Perhaps only criminals will disable the system and speed.
A speed-limiting system that cannot be compromised would seem nearly impossible to implement. And if everyone is not limited, there would be cries that the system was unfair.
June 8th, 2009 at 6:20 am
@Nancy - The phrase “enough power to get you out of trouble” originated from motor cyclists limp excuses for buying big bikes (usually to wives, etc). In reality there is no emergency situation that warrants excessive speeding.
@ Lee - Sure, you can disable any system but with a large majority of people staying at the speed limit it would be easy to pick out offenders (or perhaps with hidden speed cameras). The penalty for driving a vehicle with a disabled system should be set quite high.
The swedish came up with a sat-nav that vibrates the accelerator when you exceed the limit. Quite neat as vibration like that is hard to ignore.
Interesting that in the UK one ‘pro-motoring’ group derides speed cameras because “you can’t concentrate on your speed & look at the road ahead” while another castigated plans for speed limiters as “taking responsibility away from the driver”. Truth is, it’s hard not to speed to some extent & drivers will come up with all sorts of bull to try and justify their speeding. We need government to step in & get speeding enforced properly by whatever means.