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The Growing Divergence Between Horsepower and Speed Limits
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Comments
I would argue that all crashes are speed-related even at low speeds, but now I am splitting hairs.
I wanted a small car with good handling, good power, and good cargo capacity for roughly $18-23,000. And I wanted the power and handling so I wouldn't be forced into potentially dangerous driving situations.
Like trying to merge onto a crowded highway, only to find the car in front of you has made a full stop before merging... leaving you needing to merge onto a highway from 0 mph. That is a potentially dangerous situation, if you don't have the power, because you now place your life in the hands of other, possibly inattentive, drivers.
Is this unlikely? Not where I live. Happens to me at least twice a month, if not more often.
Or if you're on a 4-lane highway that's has relatively light traffic... and an imbecile, like the one described above, decides to pull into traffic from an on-ramp at about 10 MPH. I want a car with the handling that allows for a quick lane change without feeling like I'm either going to lose control of the vehicle or have me slide all over the interior.
Is this unlikely? HAHAHA! That's would be a funny joke here in the Baltimore-Washington area. That happens so often on MD-32 that it's not even funny.
Just two example of potentially dangerous situations, that are only dangerous if you have a slow car with poor handling. It doesn't mean I'd need a Viper or an SL-65 AMG, but something with better than average capabilities.
(BTW: I ended up buying a Volkswagen GTI to fill those needs.)
:shades:
Post 204: The speed limit on the highways we were travelling was about 1/2 and 1/2 55 mph and 65 mph. So I exceeded it the whole way, the engine never felt strained, and on the 55 stretches, I exceeded the speed limit by almost 40%.
me: Are you aware of this??
me: I couldn't agree more! Congratulations on learning a valuable lesson. You should have maximium ability to change course and speed. You've reduced your risk of being listed in some news item of a bad crash.
When someone mentioned highway design speeds, I assume they meant the actual design of the highway, which is based on part on what the anticipated speed of use is. And THAT has not changed since 1950 in the U.S.
It is 65 mph for most freeways including the interstates. On older sections of freeway that were designed for lower limits (the Pasadena freeway in LA, the section of 101 north of the Golden Gate here in Marin), the posted limit is lower (55 mph here in southern Marin).
If the driver gets the same sensation driving 90 today as he did driving 55 in 1950, it is quite likely he/she will go 90. But the highway is still designed for 65 either way. Designed, meaning the way curves are set up, the merge distances for on-ramps and lanes that are ending, that sort of thing.
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
me: NO! That is like you saying that if you have a 20-year old pair of cross-country skis, that you being an average skiier, could downhill slalom as fast as another average skiier with a modern set of downhill skis. Should there be a speed limit based on how fast you can go with the old equipment?
If a highway was built in 1950 for a speed of 65mph, that was based on a 1950 vehicle handling that stretch of roadway at a high safety level. If the designer of the highway had a 2005 vehicle to determine the same safety level, the highway would have a much higher speed limit.
As vehicles get better they can be used on the same stretch of road, at a higher speed, at the same safety level.
You can see it with the way the manufacturers are increasing hp and the way that people drive, that people want power and are willing to use it. That will drive speed limits higher, as the laws are only a reflection of the will of the majority of the people.
you: Designed, meaning the way curves are set up, the merge distances for on-ramps and lanes that are ending, that sort of thing.
me: Designed in 1950, for the technology vehicles that were on the road in 1950!
Road design basically depends on two things (once the geography is decided):
1) sightlines
2) g's
The first takes into account speed and reaction times to stuff. So yeah, if cars were slower back then, then old roads will be designed for higher speeds. But they're not designed for a regular car at the speed limit. They're designed for big rigs and/or speeders. Of the 50s, yes. A fast modern car will eat into that margin of error.
But curves (and elevation changes) are designed to be comfortable at the speeds that the engineers expect to see. Comfortable for people, not cars. Not just any people, but for Grandma. That limit of g's is not going to change with technology.
I disagree, the design of the highway contributes to the speed limit. While you might be very comfortable in your GT3 handling the curves at 200 mph, that doesn't mean that curve was designed to be taken at that speed. Line of sight as an example, might post an accident hazard at high speeds, while giving a driver ample opportunity to react to a situation at a lower speed. How fast one can go in a car is a combination of both the highway design and vehicle capabilities. These roads must be designed to support the least common denominator of driver not only the owners of high performance cars.
Well, I think the SL on freeways is too low for both the car ability and the average driver capacity.
I mentioned the capacity, because most drivers (unless handicapped or DUI) have the ability to drive well, but many don't care to use this ability.
Low speed limits makes it frustrating to go at such a pace with a high power car. My 740 is just over tickover at 80 mph/2300 RPM. I feel better at 100 mph (around 3000 Rpm) conditions allowing, needless to say.
Fuel Consumption is around 20 mpg at this pace. the best mpg I had at 100 mph was around 23 mpg with a MB C240 Estate.
How about setting Different SL depending on the car power category for freeways?
He didn't disagree with that point. (Please, let's not have another thread in which some posters debate points that others never made.)
Design speed is a function of a number of elements, many (but not all) of which are relative to the technology in use. The fact that a modern car can stop in a shorter distance and with less brake fade, and that suspensions and tires allow more nimble handling than was previously possible, are some elements that change over time.
Other elements, such as line of sight or off-camber turns, are less subject to change because technology can't help much with these. A corner, blind intersection or rising which obscured your LOS in 1950 is going to remain relatively fixed, so the improved cars won't help as much here.
The obvious winner in the above scenario is a freeway, because its design tends to eliminate the hazards of other types of roads (cross traffic, lack of seperation between directions, large variations in speed, off camber turns) and reaps the benefits of technology improvements, i.e. the ability to stop and react more quickly with few design flaws and clear visibility. So we would expect the effective design speed of a relatively modern freeway to increase over time, while that of a local road may not change quite so much. (The Pasadena Freeway mentioned above has severe limitations due to its numerous low speed curves, lack of a central shoulder, and very short entrance/exit ramps, including some with 90 degree turns, so don't expect that one to ever merit a very high limit.)
Assuming that an engineer gets to set the speed limit (as opposed to politicians who often set freeway limits somewhat arbitrarily, as is usually the case), the engineer would determine the 85th percentile travel speed, then checks for conflicts in design speed and other limitations that might call for a lower limit. We know from academic studies that drivers essentially set the 85th percentile based upon their intuitive sense of the design speed, and the vast majority of drivers get this right, which turn creates a flow of traffic which is largely traveling at a reasonable and safe speed. So over time, as the technology improves, they vote with their feet and the 85th percentile slowly edges up.
And there's no reason why the 85th percentile shouldn't change on interstates. Just so long as they can do so safely -- and the falling death and accident rates tell us that they can -- it's not a problem, and we all benefit by reduced journey times, which was a key reason why Eisenhower wanted interstates in the first place.
We are much better off than we were in the past. During the muscle car era, we had a lot of cars with strong straight-line performance that didn't have the handling or stopping power to match -- too much engine to overwhelm the other features. Newer cars are more balanced, with handling that can manage the horsepower, which benefits everyone's safety.
Apples to apples comparison. The BMW 3 series can be had with a 2.5L engine that produces 184/175 hp/torque or a 3.0L engine rated at 225/214 hp/torque. The mpg figures are identical. Someone might say that the 3.0L has a 6 speed and the 2.5L has only a 5 speed. Then look at the automatic versions, which are the exact same in gearing.
So then let's not play host.
"We know from academic studies that drivers essentially set the 85th percentile based upon their intuitive sense of the design speed"
My intuitive sense tells me at or slightly above the speed limit works very well. A speeding ticket and raised insurance rates are a great incentive to drive civily and within the law. At the other end of the spectrum causing a fatality while speeding will cause one legal grief for years to come.
We also know from information posted on the web that a number of roads have set their speed limits using this method. That would then mean only 15% of the drivers on this road speed. Right?
I think the better balanced, higher horsepower cars of today beckon some drivers to drive at speeds that are totally inappropriate. Even massive trucks like the Escalade have huge gas-guzzling engines. The drivers of these vehicles think they are in a protective cocoon.
It all depends on how the car is driven. City driving, lots of hard stop and fast go will bring out the worst of gas mileage. Going down a long hill at 60 mph with the foot off the gas will bring out the best of gas mileage. Gearing a car for great gas mileage at 55 when all the car sees is stop and go city driving should be accurately reflected in the epa figures.
Back to this again. OK, rather than drag academic studies and the professional opinion of highway engineers into it (apparently, training and professional experience don't mean much to some people), why don't you tell us where this magic, optimal speed limit is supposed to come from?
Do you think that any number will do, and that the guys with the Crown Vics and moustaches should act like brownshirts to get people to obey it? (Let's remember that during the era of the 55 mph interstate, 70-80% of drivers, including lots of ordinary folks, were breaking it routinely.)
In a democracy where government acts with the consent of the people, this obedience-with-a-stick philosophy sounds a bit more Stalinistic than it does Jeffersonian. And as the cars get better, enforcement of low limits would become more difficult, not less so.
We also know from information posted on the web that a number of roads have set their speed limits using this method. That would then mean only 15% of the drivers on this road speed. Right?
If you read the other thread (and you spent enough time there that you should have), then you know that is not true in the case of maximum freeway speed limits, because legislators set these limits, not traffic engineers. Please, let's avoid redundancy here, OK?
Apparently we have fundamental disagreements. Don't the engineers design a road with certain objectives in mind. From those objectives don't the road engineers derive the speed limit? Whether the politicians set the speed limit or not, the driving public does not determine a safe and reasonable speed limit, the engineers should.
If the engineers design a road where the speed limit is 100 mph who determines the final speed limit: 1) the government, 2) the public, 3) the engineers. We already know the answer to that.
Are you trying to kill this thread, too? This question was already addressed above in #264, and in abundance on the other thread. (Think 85th percentile = flow of traffic, i.e. something that is determined by drivers voting with their feet).
Let's try to avoid rehashing everything yet again, shall we?
Producing power requires energy -- just a body in motion uses calories, a car in motion uses fuel.
The relationship isn't necessarily linear, but all things being equal, a more powerful engine should still use more fuel than a less powerful engine for the reasons that Nitromax explained above.
That being said, driver behavior may negate some or even many of the differences, as was likely the case when you attempt to wring power out of your Metro rental in the same fashion in which you would have from your BMW. As we saw from the speed limit thread, the 55 mph speed limit did virtually nothing to create real world savings of fuel on an MPG basis -- most of the savings came from the fact that people simply drove less. The results that one may have expected to see and the actual outcome were very different.">link title
What has changed that make the newer vehicles safer on the same road? The laws of physics are still the same.
2014 Malibu 2LT, 2015 Cruze 2LT,
(OK, I'll shorten that up a bit.)
Read #264, it answers your question. And it isn't just about physics.
me: well if the system is working properly, in a democracy 1) and 2) should always be the same. At times the government (whether due to lobbyists and powerful minorities, or the personal religious beliefs of powerful politicians) ansd deviates from the desires of the public. A well-known example of this in this country was Prohibition. Whether it is "good" for the public is a secondary consideration to whether people want something. A law that people do not want can not be enforced to any great degree.
People are "voting" with their purchases of higher hp cars and driving faster that that is the direction we want to go.
Of course you would then need the power to attain flight and maintain flight. Too bad that cold-fusion experiment didn't work out, and we could all be fueling up on a quart or 2 of seawater.
Everything else in the referenced post aside, as it was a very good post, the point of freeways eliminating the hazard of large variations in speed will essentially dissolve if speed limits are allowed to increase beyond 75-80mph simply because there will always be a fairly significant % of drivers who exceed the limit by 10-20 mph regularly and those drivers who cannot or will not drive any faster than 60-65. Creating an environment where these two groups of drivers come into regular and frequent contact is increasing the risk all groups face beyond an acceptable level.
It has nothing to do with whether or not these speed differentials are happening, just with the frequency of the occurence and the judgement involved when deciding to travel at these speeds. For example, traveling a Montana freeway 40 or more miles from the nearest city at 90+ with both driver and vehicular competency may not pose excessive danger, but those same speeds on a California highway could be incredibly dangerous simply due to the amount of traffic on the road. And, if the SL was 80 on both roads, there are going to be those drivers - a majority I'd argue - that say, "Well safety be damned, if the SL is 80 then I'm going 90!!!"
But, I am getting so far off topic now.... Time to take a break from posting for a bit!
NOT
"speed limits are too low or should be repealed altogether".
The focus was on the hp, not the limits, in other words.
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
Where some confusion and perception may come in is HP ratings. Some cars with higher HP ratings may be in fact at higher rpms but the cars are actually driven at lower rpms and hence lower HP outputs - giving the perception that they may be more fuel efficient (and maybe they are if their efficiencies are better at this point than a lower rated HP engine under the same conditions).
So it is very difficult to compare a 200HP vs a 300HP directly as HP curves will be different. If efficiencies are the same - the 300HP will use more energy than the 200HP under the same conditions.
Commentary like that is unproductive. We are discussing horsepower and speed, not the 85 percentile which was originally brought up in one of your posts. So I suggest if you don't want to talk about it then don't talk about it.
You can drive whatever you want to. But if you break the law, you pay the consequences.
Yeah I think that thread has been closed down. Now if I can offer my 1 cent (thats two cents after taxes) I will say that it appears to me that all this increasing HP is pretty pointless. Lets face it even my 130 HP daily drive can maintain 80+ MPH with little effort, and in heavy city traffic you would hardly ever have the opportunity to use all a high HP engine has to offer.
that with the fact that they are usually more expensive to buy maintain and burn more fuel are high HP engines worth it? If you think so knock yourself out.
2011 Hyundai Sonata, 2014 BMW 428i convertible, 2015 Honda CTX700D
I totally disagree. If the efficiencies are the same they should use the same amount of gas. The general mindset is that with more power you have less efficiency. In the last 30 years a lot of effort has been put into making engines burn gasoline more efficiently. A good example is computer controlled fuel injection and timing. This definitely improved efficiency and a natural byproduct was more power. It was unavoidable.
Vehicles such as Z-something Corvette and proposed Camaro, both at 400-500 HP, should pay a lot for priviledge. For sake of argument, maybe Corvette with monster motor could be $1000/year. Any Bugatti that might be imported to US, with 1000 HP, might also have a $100,000 tax/year for priviledge to drive on public roads. At other end of scale, Honda Civic Sedan (not SI) or Accord Sedan with modest 4 cylinder could be perhaps $50/year. Chevy Aveo might be $25/year. Tax scale from low to high would be exponential not linear.
This would be good revenue for fixing up our national road system, would "somewhat" help ridiculous desire for some to want to go well over speed limits on interstates and would help cut down on imported oil to our nation. I know, some will say that you can drive a 4-cylinder Camry over the speed limit on interstate. But, motivation to speed like that might be reduced if you don't have a high hp car such as 300C with hemi or similar. Might save some teenage drivers from death in that they could not afford license for high horsepower cars. People would be motivated to buy cars/suvs with sensible sized engines.
me: that isn't true because so many people break the speed laws day-in and day-out and never get a speeding ticket. Unless you want to hire 5X more policemen, the speeding laws are unenforceable, except to stop an unlucky individual or 2.
I won't go into all the details (you can go back and read that), but 1 definite advantage is that more power provides for safer passing. Another is more power provides for safer merging onto a highway. Plus in any sort of emergency it is better to have more power.
But, what does "more" mean? Can you get it in a 4-cylinder in most brands of cars? What about torque curve and gearing? With good curve, torque available over wider rpm band and maybe means less need for high HP rating. Might be interesting to compare passing speed tests in Edmunds, R and T, Car and Driver, etc., for various cars, suvs.
Also, does one use power usually in an emergency or is it more common to do steering/braking? Or better yet, anticipate or be defensive.
Ok I will admit that more power provides for safer passing but lets be honest, if a pass is safe for a car with a 300 HP engine but not safe with the same car with a 200 HP engine just how safe is the pass really? In other words its a very thin line to say a pass is safer because it can be done a second or two faster.
Another is more power provides for safer merging onto a highway.
This I really don't buy, even my wifes daily drive with 100 HP (give or take 5) can get up to highway speeds on just about every on ramp and has enough response to make nessesarly adjustments.
Plus in any sort of emergency it is better to have more power.
While I agree that in some emergencies applying power is the best thing to do it is not the best thing to do in all emergencies and in some may even have detrimental effects (actually saw one like that today).
2011 Hyundai Sonata, 2014 BMW 428i convertible, 2015 Honda CTX700D
Kernick's hoping for an emergency in which Ultimate Power will save him. I don't think of emergencies so much, so my desire for power comes from situations where 100hp hasn't been enough. Namely, driving uphill in San Francisco with a fully loaded car.
Cars should have JATO units for emergencies.
2011 Hyundai Sonata, 2014 BMW 428i convertible, 2015 Honda CTX700D
me: Wow, a "Clintonism"!
you: Also, does one use power usually in an emergency or is it more common to do steering/braking?
me: That depends; on the emergency doesn't it.
me: first in any pass on a 2-lane road, you are making estimates of the distance of any oncoming traffic and their speed, and you also estimate how long it will take you to pass. I don't pass if I have to use 100% power in my pass-estimate because of the margin of error we all have (unless your Superman and can see instantly tell speed and distance of a vehicle coming towards you 1/2 mile away). You should have sufficient power to pass, and a good reserve.
you: on just about every on ramp and has enough response to make nessesarly adjustments.
me: It depends on the ramp. I know ramps that have you go around a hairpin and/or come to a stop. Or have you ever driven Rt.84 thru CT, which has extremely heavy traffic and short ramps?
you: it is not the best thing to do in all emergencies
me: no one's making that claim. More power is better simply because it covers more types of emergencies.
you: and in some may even have detrimental effects.
me: that is driver error, which we can probably agree has been around since people rode horses and tried to jump fences and hedges.
me: I'm not hoping for anything. I've stated in all different examples that it is better to have more power than less in vehicles, as it is better to have something, then not to have it and find you need or could have used it. If you're wrong in an auto, it is the most dangerous "wrong" you can have.
Power is control in all areas of life. You can pickup any newspaper and read day after day of people who did not have the power to control events. Some are injured and some are killed. It is simply better to have more power. It is illogical to think otherwise; that point is not subjective like a discussion of the ugliest car.
I'm a liberal, and even I find this to be absurd, particularly as it seems based upon the usual alarmism about horsepower, with only emotion to back it up. Until you can prove that there is a causal connection between horsepower and safety, the only thing that you have to support this position is an irrational fear of performance cars.
I find it odd that in the "land of the free, home of the brave" that irrational fears are the order of the day for some, while the allegedly pinko-commie socialist Europeans seem to have their priorities straight and have a lot more fun doing it.
A fuel tax based upon consumption would encourage fuel efficiency and reduced driving. An "L" plate system that identifies new drivers would allow police to easily observe younger drivers who tend to cause a disproportionate number of accidents, even if just piloting Escorts and Tercels.
Attacking horsepower would be no more beneficial to our safety than have been the attacks on speed. Now that we've seen that we can have higher speed limits along with improved safety and the Speed Kills! rhetoric exposed for the hysteria that it was, the Nanny Patrol wants to find another scapegoat?
unless you have an ultra weak car most cars have sufficient power to pass.
It depends on the ramp. I know ramps that have you go around a hairpin and/or come to a stop.
So do I and those are few and far between. Even then with my daily drive 99% of the time when I don't enter a highway at the speed of traffic its because there is someone a head of me driving slow.
no one's making that claim.
The claim made was "Plus in any sort of emergency it is better to have more power." I say that in many (maybe most) more power is either a non-factor or can lead to making things worse.
2011 Hyundai Sonata, 2014 BMW 428i convertible, 2015 Honda CTX700D
me: it would have been nice for you to first make a case for why higher power vehicles are "bad", before stating that they should be discouraged through taxes. I don't see the connection between power and bad. Similarly I would not tax someone more 1) who could bench-press 400Lb more than a person who can bench-press 200Lb, or 2) someone who can run 100 yd in 10 sec, instead of 15 sec.
you: Any Bugatti that might be imported to US, with 1000 HP, might also have a $100,000 tax/year for priviledge to drive on public roads.
me: But really why do you care what others drive? There are rules as to what people can buy and the manufacturers follow them. You get to make your choice what you drive, and others get to make their choice. That sounds fair to me.
me: what about taxes on speed-boats? and certainly on near 1000-hp private planes?
you: This would be good revenue for fixing up our national road system,
me: raise the gas tax, and let's have Congress stop raiding it for other purposes first.
you: would "somewhat" help ridiculous desire for some to want to go well over speed limits on interstates
me: that discussion was closed; but let's just say that what speed limit is reasonable and acceptable is subjective. No matter what side of the speed limit issue you are on, it is noted that most people show through their actions that the speed limits are too low.
you: Might save some teenage drivers from death in that they could not afford license for high horsepower cars.
me: Any vehicle made today is fast enough to kill kids showing off or experimenting. The best advice is that you don't think your kids are mature and have self-control, don't let them get a license.
me: a faster pass, especially on a 2-lane road where you have to estimate distances and speeds, or hit someone head-on, is safer the quicker you get it done. Do you agree that if you estimate the oncoming traffic to be 10-sec. away, that it is better to have the ability to pass in 5-sec. + or - 1 second rather than pass in 9 sec + or - 1 second? Then it is better to have more power. More power makes what is more difficult and dangerous, easier and safer.
Concerning on-ramps: I am not the only one who stated that they have short on-ramps, and heavy traffic to merge into. Good for you, you don't have those issues. People in the South also have trouble figuring why people drive different in snow, in the North.
you: I say that in many (maybe most) more power is either a non-factor...
me: I agree. Say 9 out of 10 emergencies power is a non-factor. And 1 out of 10 emergencies power is a useful factor. That means a lower powered vehicle is good in 9 out of 10 emergencies and a higher powered vehicle is good in 10 of 10 emergencies. The higher-powered vehicle is thus better.
you: or can lead to making things worse.
me: that is driver error, and we can postulate all sorts of things about better vehicle capabilities. You could sit here and we could discuss better brakes - that because a car brakes better it'll scare the driver and they'll release the brakes, or that better brakes will cause others to hit you because they can't stop as quick, ...
So we end up with untrained speed freaks trying bumper-bumper lane changes at 90 mph or dragracing between convoy trucks as they weave in/out of fast lane, and all too often wiping themselves or somebody else out.
Insurance companies must be taking notice of this and charging higher premiums for these over-HPed cars. Perhaps law enforcement will also write stiffer penalities for people driving higher powered cars.
Meanwhile;
Vehicle electronics now communicate with outside services such as Onstar, etc. The vehicle black boxes already record speed, miles travelled, etc. Their contents can be accessed by law enforcement in cases of accident, to determine guilty party.
It may be someday that these black boxes will be monitored, real time, by enforcement agencies who will know what car is speeding and take appropiate action, or by your insurance company who will demand to know how many miles you actually drive the vehicle.
(hold the flames; I did not say I __approve__ of this !!).
Wow!!!!. Give me some probabilities on these events occurring. Vast majority of folks will call 911 and have professionals handle. Tornados!! With weather forecasting we have now, have to be pretty stupid to be trying to outdrive tornados. Some folks need to temper tornado movies with present tornado warning weather systems.
Sounds noble. Maybe you could tell us what percent of driving you do on rural 2-lane roads in the last year.
Still missing some folks. Can anybody bring them in.