High Speed Driving In a "C"

Let me start by saying I respect everyones position so this comment is by no means to criticize. When I was 37 ( I am 65 now) I had a job that required an average of 80,000 miles per year driving and the company sent us to Bob Bondurant High Performance Driving School in AZ for a 2-day safety course. This was an eye opening experience which made me realize how much I had overestimated my capacity to react when emergency road manuvers were required. I was not alone as pretty much the whole group fo 25 students between 25 and 50 or so yrs old, got into some kind of "accident situation" trying to respond to different emergency scenarios. We practiced manuvers at speeds from 30 to 60-65 mph and the results were scary to say the least when we reviewed videos of our driving "skills". Since that time I have put into practice what I learned at the driving school regardless of the car I drive. I simply practive defensive driving at all times and do not exceed 65 mph on the freeways especially considering that, at my age, my response times most likely have significantly diminished.

 

Well said!
It was through a number of similar (though unscheduled!) experiences that I survived, that I learned to anticipate, and drive within my limitations. It was also when I learned to drive as though the car had no brakes, which has (in part) led to my finally buying a prius.

When reading some papers on driver reaction times, I found the following:

"Although most basic research finds that older people respond slower than younger ones, the data on older drivers' braking times are not entirely clear. One problem is that different studies have used different definitions of older; that is, sometimes "older means 50, sometimes it could mean 70. Moreover, some studies find no slowing of reaction time with age. Instead, they conclude that the older driver's greater experience and tendency to drive slower compensate all or in part for the decline in motor skills."

I also came across this table, which shows how far a vehicle will travel before the driver starts braking, as well as braking distances - and this is for ideal conditions.
Braking/Stopping Distances

MPH Ft./Sec. Braking Deceleration Distance Perception Reaction Distance Total (Feet)
10 14.7 5 22 27
15 22 11 33 44
20 29.3 19 44 63
25 36 30 55 85
30 44 43 66 109
35 51.3 59 77 136
40 58.7 76 88 164
45 66 97 99 196
50 73.3 119 110 229
55 80.7 144 121 265
60 88 172 132 304
65 95.3 202 143 345
70 102.7 234 154 388
75 110 268 165 433
80 117.3 305 176 481
85 124.7 345 187 532
90 132 386 198 584

 

Of course there are a number of road safety ads around that illustrate the surprising differences in stopping distances starting from different speeds. This one compares 60 km/h (37.3 mph) and 65 km/h (40.4 mph). It notes that "In the last five metres (16.4 feet) of braking, you wipe off half your speed". At the given distance demonstrated in the ad, the professor notes that "This car is still doing 32 k's (19.9 mph) when it hits" and that the other one "also hits, but only at 5 k's (3.1 mph)". It's simple physics, yet for some reason humans struggle to perceive and appreciate it.

This ad uses the same equations...

Freeways are different environments for sure, but the amount of energy you are talking about (and the significance of making even minor changes to your speed) is magnitudes greater. Unexpected events happen - be it someone else on the road, an animal, a tyre blowing, or anything - your speed has a huge impact on what happens next and the differences of different speeds are not linear.

 

If you live in over a dozen states, 75MPH isn't considered to be "high speed" driving, and while the "C" in the Priussy stands for "city" this car is certainly capable of sustained 80-mph operation.

What?
People driving 5-10 miles per hour over the speed limit????!!!!
...I'm shocked.
I don't know how to tell you this, but outside school zones.....most people drive 5-10 over.
My company Prius has a GPS monitor in it, so generally speaking, I'm at PSL, but I'll leg this out to 5 over (in the RIGHT lane!!!!!) if I'm on an interstate in a wad of traffic, since I try to be considerate to those I share the roads with.
When I'm driving a POV, I'm usually poking along at......(wait for it!..................) 5-10 over, but again, I try to be considerate to those around me being neither a tailgater nor a traffic plug.

Valid opinion, but in my opinion they might not have set the electronic speed limiter to kick in at 100+ miles per hour if the vehicle were "designed" to be driven at 60.
YMMV.

 

I'll try that table again, as it illustrates why I wouldn't drive at 80+. The stopping distance at 85 is double that at 55, which means you have to anticipate more than 500 feet down the road. The car may be designed to go that fast, but is the driver?

Braking/Stopping Distances

 

What car stops quicker than a Prius c? it is lighter than most and should stop better than most. I dissagree that the prius c is somehow not safe at higher speeds. I think all cars are not as safe at higher speeds. So that would indicate that you probably just have a general don't like people to drive at higher speeds.

 

With the right road conditions and a set of good tires, brakes, etc on a car, high speed driving should be pretty safe (check the autobahn for instance), but seeing how the American highways are deteriorating nowadays and with road rage on the rise,

I drive according to the conditions of the road and not as fast as I can possibly go, so that I can cut a few minutes/seconds off my lap time,

if everyone's doing 70+, I'll do 70+ with them too, and if I can't keep up I'll just move over for them

If it's busy, I'll play it smart and drive carefully/defensively

If it's just me out alone...I'll follow the speed limit, so I don't easily become some random cops meal

easy as that for common sense,
but some people seem to always drive like it's the end of the world and they're trying to get to wherever they're going...or they drive like they're trying to squeeze their last pint of gasoline before they reach a gas station.

been there done that, I like my money and now I have a hybrid, so drive safely

 

If enough people play by the rules, stay at or under the limit, the freeway scene occasionally deescalates, in my experience. One in a while.

 

These numbers obviously vary depending on the vehicle.

 

Well, very little, actually, for good reasons.
First, vehicle manufacturing is a very expensive business, with model volumes in the tens or hundreds of thousands. Combine that with it also being a highly competitive business, so manufacturers know the cost of every component to the dollar, probably to the cent. They aren't going to make any part of the vehicle more expensive than they have to, and they bulk purchase standard items like brake pads from suppliers who also sell to other manufacturers. Stopping distances only involve the speed, weight of vehicle, and brake components efficiency. Comparable models from competing manufacturers have very similar brakes.
Secondly, manufacturers aren't going to produce volume models with markedly varying brake efficiency, because if the car in front of you stops unexpectedly quickly, you are going to rear-end it. Safe driving is about predictibility, about judging what other vehicles around you are going to do. Manufacturers don't want lawsuits over vehicles that stop too well!

On the other hand, there is considerable driver variation - in reaction times from about 0.5 sec to 3.5 sec, in inexperienced drivers not braking hard enough, or making other poor decisions.

 

modern cars have antiskid break systems so the tires will almost lock up. This is so the car will stop as fast as possible. these cars sometimes have stability systems that also help. all this said because the main determination of how fast a car stops is its weight. a car thats weight is 1/2 of another will stop a lot shorter not 1/2 the distance but more like 110 feet instead of 160.

I don't think cars are given breaks that don't work as good as possible to avoid lawsuit. it is true a car with bigger breaks and better suspension will stop shorter but weight is more of a factor. so be careful if a big old car is following close and you have to stop quickly.

I had this happen just the other night. a deer was in the road. I hit my breaks and was able to stop way short of the deer. but the pickup behind me was going to hit us. so I let off the breaks and coasted up to the deer and stopped. the pickup still had to pull on to the shoulder and stopped with the bumper even with my rear door.

 

Virtually all current production vehicles' published road braking performance tests indicate stopping distances from 60 mph that are typically 120 to 140 feet, slightly less than half of the projected safety distances. While the figures are probably achievable, they are not realistic and certainly not average. It is very possible and probable that with some effort, the driver that attempts to be aware of braking safety procedures and practices can and should get much better braking (safely) than the guidelines used nationally, approaching that of the professionally driver published performance tests.

 

Don't let anyone force you or compel you or peer pressure you to drive at speeds you're not comfortable with. Want to drive 57 on a 65-MPH freeway (in the rightmost lane)? Do it. Saves even more gas.

 

and it won't hurt to use your hazard lights

 

Why use your hazards at 57? You are not going below the minimum speed.

 

I don't know where he/she lives but here in SoCal speed limit is 65MPH, not sure about "minimum speed" on freeway.

I think it's illegal to turn on your hazard lights to drive slow even in the right lane, hazard meant the car is not in normal driving condition.

 

US minimum is 40mph. But you are correct about the hazards.

 

i was thinking more of safety than of legality.

 

57 in a 65 isn't unsafe....