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Says who? The on-ramps aren't going to get longer just because a statistical majority decide to ignore the posted speed limit. Neither is the stopping distance of an SUV. Drivers' reaction times aren't going to get any shorter. There are realities of physics, engineering, and human performance that we ignore at our literal peril.
There is a traffic engineering standard that says this. Some states make it a law. Not sure about Michigan.
Does anyone really care about this? It makes no difference to me. If the freeway is clear and conditions are safe, I drive 75-80 or 85 if I am in a rush and in a good vehicle and conditions are otherwise safe. If traffic, I go with he flow whether that is 65, 70, 75, or 80. I do not really care what the posted speed limit is. I will drive at the speed I am comfortable and feel is safe for the conditions. Speed limits on freeways are never enforced anyway, just don't be the fastest moving car out there and you are good.
Stopping distance of an SUV does not dictate speed limits. A safe stopping distance must be maintained for the speed you are traveling and the conditions. If the car in front of you is going 80, you can go 80. Just leave 8-10 car lengths of space. If they are going 70, you can still go 80 until you get within 8 - 10 car lengths, then you must other pass them or slow down. However speed limit is not dictated by stopping distances, it is all relative. You can go any speed in an SUV as log as you leave enough space between you and the next car. My rule of thumb is 1 car length for every 10MPH plus some if you are in a heavy vehicle or something that does not stop that well. double or triple that for snow. For ice, I pretty much just do not want anyone in front of me within sight. Of course, you are not going to drive with any speed on ice anyway.
I really think speed limit should be dictated by your car and ts condition. That would require regular inspections and then you get (or lose) a stickier indicating your car is safe to go up to X speed. I really have no problem with someone driving a ca 90 mph if they are practicing good driving and their car is designed to go 130 and well maintained. I have a problem with someone in a beat up Ford Focus with bad control arms and/or tie rods flying along at high speeds. It woudl be complicated and probably too expensive to ever implement, but I think it woudl be a good way to allow higher speed driving. Maybe test the drivers too. this might be more practical as technology improves. Rather than a sticker, the car can broadcast to the police car, this car/driver is certified to go up to 65 MPH, this car is certified to 90 MPH. Maybe we can designate the fast lane as an express lane where you have to have the sticker and cannot drive slower than 75 unless there is a traffic issue. Kind of like California's car pool lanes or the toll express lanes on some freeways. Frankly, I think most people who want to drive fast woudl be willing to pay a toll or an annual fee to be able to drive up to 90 MPH in a separate lane.
There is a traffic engineering standard that says this. Some states make it a law. Not sure about Michigan.
Does anyone really care about this? It makes no difference to me. If the freeway is clear and conditions are safe, I drive 75-80 or 85 if I am in a rush and in a good vehicle and conditions are otherwise safe. If traffic, I go with he flow whether that is 65, 70, 75, or 80. I do not really care what the posted speed limit is. I will drive at the speed I am comfortable and feel is safe for the conditions. Speed limits on freeways are never enforced anyway, just don't be the fastest moving car out there and you are good.
Stopping distance of an SUV does not dictate speed limits. A safe stopping distance must be maintained for the speed you are traveling and the conditions. If the car in front of you is going 80, you can go 80. Just leave 8-10 car lengths of space. If they are going 70, you can still go 80 until you get within 8 - 10 car lengths, then you must other pass them or slow down. However speed limit is not dictated by stopping distances, it is all relative. You can go any speed in an SUV as log as you leave enough space between you and the next car. My rule of thumb is 1 car length for every 10MPH plus some if you are in a heavy vehicle or something that does not stop that well. double or triple that for snow. For ice, I pretty much just do not want anyone in front of me within sight. Of course, you are not going to drive with any speed on ice anyway.
I really think speed limit should be dictated by your car and ts condition. That would require regular inspections and then you get (or lose) a stickier indicating your car is safe to go up to X speed. I really have no problem with someone driving a ca 90 mph if they are practicing good driving and their car is designed to go 130 and well maintained. I have a problem with someone in a beat up Ford Focus with bad control arms and/or tie rods flying along at high speeds. It woudl be complicated and probably too expensive to ever implement, but I think it woudl be a good way to allow higher speed driving. Maybe test the drivers too. this might be more practical as technology improves. Rather than a sticker, the car can broadcast to the police car, this car/driver is certified to go up to 65 MPH, this car is certified to 90 MPH. Maybe we can designate the fast lane as an express lane where you have to have the sticker and cannot drive slower than 75 unless there is a traffic issue. Kind of like California's car pool lanes or the toll express lanes on some freeways. Frankly, I think most people who want to drive fast woudl be willing to pay a toll or an annual fee to be able to drive up to 90 MPH in a separate lane.
Depending on how much they charge me, I would. Much less stressful than looking out for speed trapping cops.
8-10 car lengths at 80 mph is no where near sufficient. That's about 120'. Your reaction distance at 80 mph is going to be about 115', then tack on your braking distance to 0 being 320' and, well.. you just rear-ended someone, even if they only braked down to 50-60 mph.
Yeah, sure, if there's no one around go 80, go 90 for all I care, but we all know that all increasing the speed limit does is increase the number of douchebags weaving in an out of traffic at a tight-packed 65 MPH moving freeway traffic, because, "What? It's legal? I can go 75." Metro freeways were designed and engineered for 55 mph traffic. Increasing it to 65 would've been reasonable simply due to technology advances, 70 is.. well.. I'm not a huge fan of going 70 on some of the freeways here, 75 is stupid.
Sure, when you get on I-75 North past Sashabaw that kind of speed makes sense, especially where you've got 4 lanes and no traffic, between Flint and Saginaw, but in the city that's the kind of travel rate that maybe won't get you in trouble most of the time, but it'll catch up with you eventually - regardless of if you're in a Cobalt or a Corvette.
There is a traffic engineering standard that says this. Some states make it a law. Not sure about Michigan.
Does anyone really care about this? It makes no difference to me. If the freeway is clear and conditions are safe, I drive 75-80 or 85 if I am in a rush and in a good vehicle and conditions are otherwise safe. If traffic, I go with he flow whether that is 65, 70, 75, or 80. I do not really care what the posted speed limit is. I will drive at the speed I am comfortable and feel is safe for the conditions. Speed limits on freeways are never enforced anyway, just don't be the fastest moving car out there and you are good.
Stopping distance of an SUV does not dictate speed limits. A safe stopping distance must be maintained for the speed you are traveling and the conditions. If the car in front of you is going 80, you can go 80. Just leave 8-10 car lengths of space. If they are going 70, you can still go 80 until you get within 8 - 10 car lengths, then you must other pass them or slow down. However speed limit is not dictated by stopping distances, it is all relative. You can go any speed in an SUV as log as you leave enough space between you and the next car. My rule of thumb is 1 car length for every 10MPH plus some if you are in a heavy vehicle or something that does not stop that well. double or triple that for snow. For ice, I pretty much just do not want anyone in front of me within sight. Of course, you are not going to drive with any speed on ice anyway.
I really think speed limit should be dictated by your car and ts condition. That would require regular inspections and then you get (or lose) a stickier indicating your car is safe to go up to X speed. I really have no problem with someone driving a ca 90 mph if they are practicing good driving and their car is designed to go 130 and well maintained. I have a problem with someone in a beat up Ford Focus with bad control arms and/or tie rods flying along at high speeds. It woudl be complicated and probably too expensive to ever implement, but I think it woudl be a good way to allow higher speed driving. Maybe test the drivers too. this might be more practical as technology improves. Rather than a sticker, the car can broadcast to the police car, this car/driver is certified to go up to 65 MPH, this car is certified to 90 MPH. Maybe we can designate the fast lane as an express lane where you have to have the sticker and cannot drive slower than 75 unless there is a traffic issue. Kind of like California's car pool lanes or the toll express lanes on some freeways. Frankly, I think most people who want to drive fast woudl be willing to pay a toll or an annual fee to be able to drive up to 90 MPH in a separate lane.
They can't lengthen or shorten all the on-ramps, etc., every time the speed limit changes. The highways were engineered for a specific speed limit, which may have referenced that 85th percentile thing when they were built for all I know, but is now literally set in concrete.
As for the rest, that's all reasonable, but deer, drunks, inexperienced drivers, those prone to road rage, and many others don't always act reasonably. Increasing the speed limits ups the ante when something unexpected happens. I remember a crash I was in when the driver was going over 80 and didn't notice in time that traffic on the highway had come to a stop due to construction. He slammed on the brakes but was unable to come to a complete stop before slamming into the last car in a line of stopped vehicles. Fortunately no one was seriously hurt.
I noticed that you mentioned on another thread that increasing the speed limit may contribute to the flight from the city and inner core to outer suburbs, which is not a safety issue per se, but is still something to consider.
8-10 car lengths at 80 mph is no where near sufficient. That's about 120'. Your reaction distance at 80 mph is going to be about 115', then tack on your braking distance to 0 being 320' and, well.. you just rear-ended someone, even if they only braked down to 50-60 mph.
Yeah, sure, if there's no one around go 80, go 90 for all I care, but we all know that all increasing the speed limit does is increase the number of douchebags weaving in an out of traffic at a tight-packed 65 MPH moving freeway traffic, because, "What? It's legal? I can go 75." Metro freeways were designed and engineered for 55 mph traffic. Increasing it to 65 would've been reasonable simply due to technology advances, 70 is.. well.. I'm not a huge fan of going 70 on some of the freeways here, 75 is stupid.
Sure, when you get on I-75 North past Sashabaw that kind of speed makes sense, especially where you've got 4 lanes and no traffic, between Flint and Saginaw, but in the city that's the kind of travel rate that maybe won't get you in trouble most of the time, but it'll catch up with you eventually - regardless of if you're in a Cobalt or a Corvette.
You are assuming they are instantly at zero, which they will not be. All you really need is enough space to accommodate the delay in your reaction time and any possible difference between their braking speed and yours.If my braking distance is 320 and theirs is 298 feet, I am fine. In fact I am fin even if their braking distance is 298 feet and mine is 410 feet. Yes, if they suddenly slam into a stationary object without braking, you are sol. The is why they have shoulders and medians. I have been driving on freeways the same way for 38 years. Number of rear ending people 0; number of close calls 0.
The freeways were actually not designed in engineered for 55 mph traffic. First freeways are not engineered for a particular speed for the most part (ramps are different and a few curves where a specific suggested speed limit is listed, but even those are designed to be safe for a 45' RV, a 60' semi or an ungainly thing like a hummer. Most cars are safe at considerably higher than the recommended speeds.) secondly most of the freeways were laid out long before the 55 mph speed limit and/or were reconstructed after it went away. There is one location in Michigan that I know of where speed over 70 could be a problem and it is clearly marked.
In general on the freeways, people who go fast drive around 80 to 85. The drive that speed regardless of the posted limit. What a lower posted speed does is makes some people think it is ok for them to cruise along in the left lane at 70 MPH which would create a problem (more likely an annoyance than an actual problem). the drives who drive 80 MPH or 85 MPH are not going to start driving 100 MPH if the speed limits change to 75.
Says who? The on-ramps aren't going to get longer just because a statistical majority decide to ignore the posted speed limit. Neither is the stopping distance of an SUV. Drivers' reaction times aren't going to get any shorter. There are realities of physics, engineering, and human performance that we ignore at our literal peril.
Cool. I say we set it at 45 and see where that gets us.
They can't lengthen or shorten all the on-ramps, etc., every time the speed limit changes.
You're forgetting that the on-ramps were built when the average 0-60 time was substantially less than it is today. What was the time it took a family sedan to get up to highway speeds back in the 50s? 15 seconds? How about today?
At 8 car lenghts, you're maybe 100 feet behind them. If they're going 80 and they slam on their brakes, you're still going 80 mph (117 feet per second) when you realize and they've slowed down to 55 mph (80 fps). I don't want to do the calculus, but you're now ~65-70 feet behind them before you even touch your brake pedal. This is fine, assuming they don't slow below 55 - which is typical on free flowing freeways, but if they have to slow even further you'll be approaching at an ever increasing rate of 40 feet per second when they hit their brakes and probably 60-70 feet per second as they've slowed down to 45, 35, 25.. or more, as you can brake much more quickly from 55 to 30 (or 30 to 0) than you can from 80 to 55.
I mean, yeah, I guess you're right - you can probably go years and years without getting in a wreck by following 8-10 car lengths at 80 mph, as people almost never brake from 80 to 0, but eventually it can happen. At 65 or 70 mph though, you're much safer. How much time do you save by driving 80 instead of 70? Well, you can drive from Downtown Detroit to Downtown Lansing 9 minutes faster. Is that really worth it? Couldn't you simply leave 9 minutes earlier?
(Ugh, my former WRX driving 22 year old self is rolling over in his grave right now...)
I noticed that you mentioned on another thread that increasing the speed limit may contribute to the flight from the city and inner core to outer suburbs, which is not a safety issue per se, but is still something to consider.
It increases the reasonable range for a commute, so it cold open up Fenton, Fowlerville, Pinkney, and the like as the next targets of Yppification.
At 8 car lenghts, you're maybe 100 feet behind them. If they're going 80 and they slam on their brakes, you're still going 80 mph (117 feet per second) when you realize and they've slowed down to 55 mph (80 fps). I don't want to do the calculus, but you're now ~65-70 feet behind them before you even touch your brake pedal. This is fine, assuming they don't slow below 55 - which is typical on free flowing freeways, but if they have to slow even further you'll be approaching at an ever increasing rate of 40 feet per second when they hit their brakes and probably 60-70 feet per second as they've slowed down to 45, 35, 25.. or more, as you can brake much more quickly from 55 to 30 (or 30 to 0) than you can from 80 to 55.
I mean, yeah, I guess you're right - you can probably go years and years without getting in a wreck by following 8-10 car lengths at 80 mph, as people almost never brake from 80 to 0, but eventually it can happen. At 65 or 70 mph though, you're much safer. How much time do you save by driving 80 instead of 70? Well, you can drive from Downtown Detroit to Downtown Lansing 9 minutes faster. Is that really worth it? Couldn't you simply leave 9 minutes earlier?
(Ugh, my former WRX driving 22 year old self is rolling over in his grave right now...)
The problem is what you posit cannot happen. They cannot just slow from 80 to 55 without my noticing. First the y will slow to 70 and by that time I will be braking. Then they will slow to 60 and I will be at maybe 65 or less if I am braking harder than they,etcetera. Even if they absolutely slam on their brakes, I can do the same. 7 - 8 car lengths is plenty. As you get more experience driving, you will see how this works and develop a distance you are comfortable with. However you are also going to find most people leave less than 2 car lengths at any speed. At least in Michigan.
You will also learn leaving even 8 - 10 car lengths is nearly impossible on a freeway. If you leave that much space, people will start going around you, Then you will need to slow down to leave more space, then more people will go around you, then you will slow again to make space for the cars that just filled in your 10 car length safety zone, soon you will be going 15 mph just to make room for the flow of cars going around you. If you want to try leaving 15 to 20 lar lengths on the freeway, I was to watch, it will be amusing.
As mentioned, the shoulder is what prevents constant crashes. That and the fact that it is unusual for there to be any braking.
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