[Ladogaboy]

We seem to keep coming back to discussions about the Bolt EV's freeway efficiency, and I maintain that (based on my experiences) the Bolt EV's efficiency up to 75 mph is very similar to my first generation Volt. In a recent test of the Ampera-E, Bjorn Nyland had measured its 75 mph cruising efficiency at 2.9-3 mi/kWh, which is significantly lower than what I typically see. It turns out that the Ampera-E uses different tires, and that could account for some of the differences in efficiency.

Personally, I don't think it accounts for the ~15% difference in efficiency, but none of this is rigorous, scientific testing. Regardless, I just so happened to have a recent trip that allowed me to track my real-world efficiency by hoping on the freeway almost immediately (normally, I have a 20 to 30 mile drive first) and driving nearly 100% of the first leg at 70-75 mph freeway speeds.

Despite having brand new tires, the efficiency was still in line with what I typically see. After 84 miles of driving, I had an efficiency of 3.3 mi/kWh, including close to 5% of the energy being used for climate control. That very closely aligns with the ~3.5 mi/kWh I see at close to 70 F ambient temperatures without climate control usage.

 

[Raymondjram]

Drive slower, save energy and lives.

 

[obermd]

Drive slower, save energy and lives.

The safety of higher speeds depends on the road. When Colorado raised the I-25 speed limit from 65 to 75 there was a reduction in crashes. This is because the range of speeds dropped. The slowest cars sped up to around 70 (from 60 or even 55) and the fastest cars slowed down from around 90 to 80 or so. On the interstate, the variance in speeds has a director correlation to the number of crashes.

Accidents occurring at higher speeds tend to be more dangerous due to more kinetic energy involved, but the reduction in accidents seen on I-25 more than countered the severity of accidents, improving overall road safety.

 

[Dutch]

Drive slower, save energy and lives.

There's always gotta be one.


Have you ever been to LA?

 

[Steverino]

Nice to know that my Bolt EV will do well if I ever drive that fast. I typically do 60 MPH. For my drives, arriving 6 minutes earlier does not mean a lot. But for very long drives it's a different story. Of course, those drives will rake longer anyway due to recharging stops. Hurry up to wait?

 

[FI Spyder]

Driving speed vs. time saved. I remember someone did a test (I think it might have been an automotive magazine) where they had two Mercedes drive the same route from New York city to Los Angeles. One meticulously stuck to the speed limit and the other could speed as much as he wanted. The car sticking to speed limits arrived 4 hours later, not much considering the distance traveled.

 

[Ladogaboy]

Nice to know that my Bolt EV will do well if I ever drive that fast. I typically do 60 MPH. For my drives, arriving 6 minutes earlier does not mean a lot. But for very long drives it's a different story. Of course, those drives will rake longer anyway due to recharging stops. Hurry up to wait?

It's true, but ironically, best trip speeds are still achieved by driving as fast as is legal in most cases. Even with the Bolt EV's "slow" 45-55 kW charge rates, it is faster to drive as fast as is legal. On 70 mph roads with 125 A charging available, my average trip speed is about 50 mph. It should bump up a bit when 150 A charging is available.

The point of diminishing returns for the Bolt EV on 125 A charging doesn't occur until almost 80 mph sustained driving (though weather can impact that). When 150 A charging becomes available, that should bump up even further. Basically, for those of us with 85 mph posted speeds, as long as DCFC is available, we shouldn't worry about driving the speed limit in our Bolt EVs.

Obviously, faster charging would be nice, but I'm just working with the current reality.

 

[obermd]

Driving speed vs. time saved. I remember someone did a test (I think it might have been an automotive magazine) where they had two Mercedes drive the same route from New York city to Los Angeles. One meticulously stuck to the speed limit and the other could speed as much as he wanted. The car sticking to speed limits arrived 4 hours later, not much considering the distance traveled.

And most of that four hour difference occurred in the east where speed limits were artificially low for the 70 MPH design of the interstate system. I suspect the time difference would be even less now that most of the eastern states have raised their speed limits to the road design speed.

 

[Qinsp]

Thanks!

Even at 3.3 mi / kWh that's not bad. EPA tests for highway says 3.2mi/kWh but IIRC, that's from the wall.
A Euro test of the Ampera said it achieved 99% of the WLTP advertised range. This was higher than the Tesla MS/X rating.
Sadly, the Jaguar i-Pace only registered 65% of advertised WLTP but the car was a prototype and not allowed to use the ECO mode.

Rumor is the sales of the i-Pace could be delayed in the UK until they get closer to the advertised range. Top Gear found that you must slow down to 47 mph to achieve full WLTP rating. EPA numbers are not filed yet.

The furthest trip I would ever need to make would be 240 miles in an EV. So the Bolt is winning even though the usable battery on the i-Pace is 84.7 kWh, but it weighs a lot, like close to 4800lb.

 

[Don M]

There's always gotta be one.

Have you ever been to LA?

Has he ever been away from Puerto Rico? Doing only 75 mph on the I-285 loop around Atlanta means you're very likely to get run over and killed, but 75 on most roads in Puerto Rico probably is too fast for safety - I've been there several times and travelend from one end of the island to the other

Don

 

[Qinsp]

The safety of higher speeds depends on the road. When Colorado raised the I-25 speed limit from 65 to 75 there was a reduction in crashes. This is because the range of speeds dropped. The slowest cars sped up to around 70 (from 60 or even 55) and the fastest cars slowed down from around 90 to 80 or so. On the interstate, the variance in speeds has a director correlation to the number of crashes.

Accidents occurring at higher speeds tend to be more dangerous due to more kinetic energy involved, but the reduction in accidents seen on I-25 more than countered the severity of accidents, improving overall road safety.

There was a study years ago when 55 was still law. People would drive 70-75 average anyways on empty highways. When the changed the speed limit to 65, they would drive 70-75 on the same highway. When they raised it to 70, they drove 70-75.

But cars are now smoother, better handling, better tires, better brakes. So I would not be surprised if the average is... 70-75. Because it was and is the drivers comfort level, not the 200+ mph car technology that governs our comfort zone.

 

[JRRF]

And most of that four hour difference occurred in the east where speed limits were artificially low for the 70 MPH design of the interstate system. I suspect the time difference would be even less now that most of the eastern states have raised their speed limits to the road design speed.

The original design was for 70 mph, but the current state of repair, and volume of cars, makes a safe speed much lower in much of the country.

I've driven the Denver to Cheyenne route many times, and once north of Longmont, sure you can go faster. But you couldn't do that anywhere on I-95.

In addition, in the 50's and 60's when the interstate system was built, drivers had nothing else to do but watch the road. Today nearly every car has a touch screen, and every driver has a cell phone screen. Faster speeds mean each glance at something other than the road puts you farther down the road, and nearer to something unexpected.

 

[JRRF]

There was a study years ago when 55 was still law. People would drive 70-75 average anyways on empty highways. When the changed the speed limit to 65, they would drive 70-75 on the same highway. When they raised it to 70, they drove 70-75.

But cars are now smoother, better handling, better tires, better brakes. So I would not be surprised if the average is... 70-75. Because it was and is the drivers comfort level, not the 200+ mph car technology that governs our comfort zone.

On the autobahn the average speed is about 80 mph. Most cars are not particularly stable past that. Nor is it comfortable driving faster than that. Above that speed the amount of attention required is draining, because everything happens very fast.

 

[obermd]

There was a study years ago when 55 was still law. People would drive 70-75 average anyways on empty highways. When the changed the speed limit to 65, they would drive 70-75 on the same highway. When they raised it to 70, they drove 70-75.

But cars are now smoother, better handling, better tires, better brakes. So I would not be surprised if the average is... 70-75. Because it was and is the drivers comfort level, not the 200+ mph car technology that governs our comfort zone.

The other thing that happened was the speed outliers, both low and high, came closer together. In other words the speed range went from 90 - 55 (35 MPH) to 80 - 65 (15 MPH). This translates into fewer quick lane changes and cars dodging in and out, making the highway safer.

 

[obermd]

The original design was for 70 mph, but the current state of repair, and volume of cars, makes a safe speed much lower in much of the country.

I've driven the Denver to Cheyenne route many times, and once north of Longmont, sure you can go faster. But you couldn't do that anywhere on I-95.

In addition, in the 50's and 60's when the interstate system was built, drivers had nothing else to do but watch the road. Today nearly every car has a touch screen, and every driver has a cell phone screen. Faster speeds mean each glance at something other than the road puts you farther down the road, and nearer to something unexpected.

True on both counts, especially for I-95 (and I-5 for that matter), but for the east-west routes other than the I-80/90, 70 to 75 is still a reasonable speed once you get more than an hour or so away from the coastal megalopolis.

 

[Sean Nelson]

The safety of higher speeds depends on the road. When Colorado raised the I-25 speed limit from 65 to 75 there was a reduction in crashes. This is because the range of speeds dropped. The slowest cars sped up to around 70 (from 60 or even 55) and the fastest cars slowed down from around 90 to 80 or so. On the interstate, the variance in speeds has a director correlation to the number of crashes.

Accidents occurring at higher speeds tend to be more dangerous due to more kinetic energy involved, but the reduction in accidents seen on I-25 more than countered the severity of accidents, improving overall road safety.

Why do I find it highly annoying that it's the speed limit drivers that are criticized for creating a hazard rather than the speeders? Especially when there are slower speed limits for trucks and you can easily trail a ways behind one of these and be of no more hindrance to anyone else than the truck itself is.

 

[Dutch]

Why do I find it highly annoying that it's the speed limit drivers that are criticized for creating a hazard rather than the speeders? Especially when there are slower speed limits for trucks and you can easily trail a ways behind one of these and be of no more hindrance to anyone else than the truck itself is.

Oh I've seen a couple of astounding pileups because of Rigs pulling into the passing lane before trying a hill and suddenly reducing speed.... wham, wham, wham.

Look up I81 in Harrisonburg VA. We've had a hell of a time with that lately. So much so that VA changed it's laws making it actively illegal to sit in the left lane if not passing.

 

[Ladogaboy]

Why do I find it highly annoying that it's the speed limit drivers that are criticized for creating a hazard rather than the speeders? Especially when there are slower speed limits for trucks and you can easily trail a ways behind one of these and be of no more hindrance to anyone else than the truck itself is.

I agree. Disparate speeds do cause a significant number of accidents; however, it is hard to find fault with someone who is going the speed limit, even though everyone else is going 15 mph faster.

To me, it's not just how fast the person is going, but where they are going that speed. I would say that, even exactly following the speed limit, it is not acceptable for someone to be in the left-most lane unless they are actively passing someone (after which, the immediately need to merge to the right). And if someone is going noticeably slower than the speed limit, they do need to be in the right lane. To Dutch's point, I've had semis doing 40 mph on a 70 mph freeway pull out in front of me because the semi ahead of them was doing 35 mph. That creates a super dangerous situation.

 

[Sean Nelson]

I've had semis doing 40 mph on a 70 mph freeway pull out in front of me because the semi ahead of them was doing 35 mph. That creates a super dangerous situation.

I cut my teeth here in British Columbia driving mountain highways with one lane in each direction where slow logging trucks (going uphill OR downhill!) would create huge lineups of impatient drivers who would take crazy chances trying to pass a little too close to blind corners. Your land of 3-lanes + truck climbing lane sure doesn't scare me!

 

[hellsop]

Has he ever been away from Puerto Rico? Doing only 75 mph on the I-285 loop around Atlanta means you're very likely to get run over and killed

I'd love to see evidence of this. Any collision where the slower driver ahead was ticketed as "at fault" would do. Or anyone ticketed for obstructing traffic at speed limit +/- 5 MPH while not in the leftmost lane would be fine too.