5 ms·

Today's cars are much safer than the cars of the 70s at higher speeds. Not only do they better protect the occupants in an impact but they steer better, break

Today's cars are much safer than the cars of the 70s at higher speeds. Not only do they better protect the occupants in an impact but they steer better, break better and are far more stable. Add to that better fuel efficiencies and it's hard to argue that we need the same speed limits. 55 was a response to the oil crisis but it also reflected automobile engineering of the time.

javagram 7y ago
I have a 2010 model car and I still seem to get significantly better gas mileage around 55-65 mph than I do around 70-75, although I haven’t measured it scientifically. Isn’t this a function of wind resistance physics that can’t be solved, just mitigated? As driving automation increases and the threat of climate change and CO2 emissions looms larger, automated cars could drive at current speed limits without getting impatient like a human driver, improving both efficiency and safety.
- lm28469 7y ago
  It does. Almost any car will be more efficient around 50-60mph. But it only matters on highway where the bottleneck is due to aerodynamism, at lower speed you might be less efficient at 20mph than 30mph for example. https://en.m.wikipedia.org/wiki/Fuel_economy_in_automobiles https://en.m.wikipedia.org/wiki/Fuel_economy_in_automobiles
- ska 7y ago
  Isn’t this a function of wind resistance physics that can’t be solved, just mitigated? Yes, this is fundamental; roughly power required is proportional to cubed velocity. Improved coeff of friction helps, but you can't get away from this. Eventually air friction is the completely dominant force. So at highway speeds, absent some rare gearing issues causing inefficient fueling, faster means less efficient. This is also why the fastest "hypercars" are pushing on order of 1000 hp. At lower speeds, all sorts of other issues kick in (and idling is its own issue)
  - mywittyname 7y ago
    A demonstration of this fact can be found in a list of fastest production cars in the world: https://en.wikipedia.org/wiki/Production_car_speed_record https://en.wikipedia.org/wiki/Production_car_speed_record The RUF (Porsche) needs 460hp to break 213mph. The next record breaker needs 618hp to break 221mph. The 241mph record is made with 806hp. This continues incrementally until the current record holder, which needs 1350hp to hit 278mph. It took three times as much power and three decades of computational advancement to build a car that could go a mere 65mph faster than the 1983 record breaker. Side note: the listed horsepower numbers before 1980s are basically made up. You can safely assume SAE J2723 horsepower (what cars use today) is ~60-75% of published value for cars older than 1980 (and about ~80-95% for cars between 1980 and 2005).
- rtkwe 7y ago
  It's a bit of both but yes velocity dominates the drag forces. You can reduce the wind resistance of vehicles reducing their coefficient of drag but the dominant factor as you reach higher speeds is velocity which increases as a square where the drag coefficient is only directly proportional to the end drag. There are definitely limits to how low drag we can make the normal passenger sedan without drastically changing it's functional form. If we move to a more infrastructure style car transport where you just subscribe or have access to (depending on where we end up on the public-private spectrum) there's probably a lot of gains we can still make that will make cars much uglier (to our current eyes) but more aerodynamic.
bryanlarsen 7y ago
OTOH, during the 70s drunk driving, heavy smoking, not using seatbelts and a whole host of other very dangerous activities were socially acceptable.
jonstewart 7y ago
Yes, they're much safer for the occupants. They're probably less safe for pedestrians and cyclists hit by them, considering the increase in mass and height.
- jcoffland 7y ago
  > considering the increase in mass and height. Most of today's cars are significantly less massive even if their size is larger.
  - jonstewart 7y ago
    My first car was an '84 Ford Crown Vic LTD, that beautiful monstrosity of a two door coupe. It was ~215 inches long and was made out of ~3650 lbs of Detroit steel. I now drive a 2015 Ford Escape, which is 178 inches long and weighs ~3550 pounds. Similar-sized cars are probably lighter nowadays, but the overwhelming shift towards SUVs holds back the average mass. Now I'm misty-eyed, thinking of my beautiful LTD... a completely inappropriate car in 2019, but so much fun to drive.
- mywittyname 7y ago
  Every new car is designed with pedestrian safety as a concern. Pedestrian safety regulations are the major reason all cars share the same profile. Designers don't have much leeway when it comes to the shape of a car because all the panels need sufficient cushion and be angled such that pedestrians are deflected, and there's only so many ways to accomplish that. So designers focus on what they can change, which is pretty much grills, tail lights and door creases.
  - jonstewart 7y ago
    I am sure there are design considerations, but the IIHS believes there’s a link between rising pedestrian deaths and the rising proportion of cars on the road being SUVs. Source: https://usa.streetsblog.org/2018/05/09/study-links-rise-of-suvs-to-the-pedestrian-safety-crisis/ https://usa.streetsblog.org/2018/05/09/study-links-rise-of-s...
goodcanadian 7y ago
A bit of pedantry, but I see it a lot on HN. You definitely do not want your car to break. You may want it to brake.
- bradknowles 7y ago
  I dunno. If I hit a hard barrier, I'd prefer that the car break and disintegrate and dissipate all that energy, as opposed to transferring all that energy into me as the occupant.

javagram 7y ago

I have a 2010 model car and I still seem to get significantly better gas mileage around 55-65 mph than I do around 70-75, although I haven’t measured it scientifically. Isn’t this a function of wind resistance physics that can’t be solved, just mitigated? As driving automation increases and the threat of climate change and CO2 emissions looms larger, automated cars could drive at current speed limits without getting impatient like a human driver, improving both efficiency and safety.

lm28469 7y ago
It does. Almost any car will be more efficient around 50-60mph. But it only matters on highway where the bottleneck is due to aerodynamism, at lower speed you might be less efficient at 20mph than 30mph for example. https://en.m.wikipedia.org/wiki/Fuel_economy_in_automobiles https://en.m.wikipedia.org/wiki/Fuel_economy_in_automobiles
ska 7y ago
Isn’t this a function of wind resistance physics that can’t be solved, just mitigated? Yes, this is fundamental; roughly power required is proportional to cubed velocity. Improved coeff of friction helps, but you can't get away from this. Eventually air friction is the completely dominant force. So at highway speeds, absent some rare gearing issues causing inefficient fueling, faster means less efficient. This is also why the fastest "hypercars" are pushing on order of 1000 hp. At lower speeds, all sorts of other issues kick in (and idling is its own issue)
- mywittyname 7y ago
  A demonstration of this fact can be found in a list of fastest production cars in the world: https://en.wikipedia.org/wiki/Production_car_speed_record https://en.wikipedia.org/wiki/Production_car_speed_record The RUF (Porsche) needs 460hp to break 213mph. The next record breaker needs 618hp to break 221mph. The 241mph record is made with 806hp. This continues incrementally until the current record holder, which needs 1350hp to hit 278mph. It took three times as much power and three decades of computational advancement to build a car that could go a mere 65mph faster than the 1983 record breaker. Side note: the listed horsepower numbers before 1980s are basically made up. You can safely assume SAE J2723 horsepower (what cars use today) is ~60-75% of published value for cars older than 1980 (and about ~80-95% for cars between 1980 and 2005).
rtkwe 7y ago
It's a bit of both but yes velocity dominates the drag forces. You can reduce the wind resistance of vehicles reducing their coefficient of drag but the dominant factor as you reach higher speeds is velocity which increases as a square where the drag coefficient is only directly proportional to the end drag. There are definitely limits to how low drag we can make the normal passenger sedan without drastically changing it's functional form. If we move to a more infrastructure style car transport where you just subscribe or have access to (depending on where we end up on the public-private spectrum) there's probably a lot of gains we can still make that will make cars much uglier (to our current eyes) but more aerodynamic.

bryanlarsen 7y ago

OTOH, during the 70s drunk driving, heavy smoking, not using seatbelts and a whole host of other very dangerous activities were socially acceptable.

jonstewart 7y ago

Yes, they're much safer for the occupants. They're probably less safe for pedestrians and cyclists hit by them, considering the increase in mass and height.

jcoffland 7y ago
> considering the increase in mass and height. Most of today's cars are significantly less massive even if their size is larger.
- jonstewart 7y ago
  My first car was an '84 Ford Crown Vic LTD, that beautiful monstrosity of a two door coupe. It was ~215 inches long and was made out of ~3650 lbs of Detroit steel. I now drive a 2015 Ford Escape, which is 178 inches long and weighs ~3550 pounds. Similar-sized cars are probably lighter nowadays, but the overwhelming shift towards SUVs holds back the average mass. Now I'm misty-eyed, thinking of my beautiful LTD... a completely inappropriate car in 2019, but so much fun to drive.
mywittyname 7y ago
Every new car is designed with pedestrian safety as a concern. Pedestrian safety regulations are the major reason all cars share the same profile. Designers don't have much leeway when it comes to the shape of a car because all the panels need sufficient cushion and be angled such that pedestrians are deflected, and there's only so many ways to accomplish that. So designers focus on what they can change, which is pretty much grills, tail lights and door creases.
- jonstewart 7y ago
  I am sure there are design considerations, but the IIHS believes there’s a link between rising pedestrian deaths and the rising proportion of cars on the road being SUVs. Source: https://usa.streetsblog.org/2018/05/09/study-links-rise-of-suvs-to-the-pedestrian-safety-crisis/ https://usa.streetsblog.org/2018/05/09/study-links-rise-of-s...

goodcanadian 7y ago

A bit of pedantry, but I see it a lot on HN. You definitely do not want your car to break. You may want it to brake.

bradknowles 7y ago
I dunno. If I hit a hard barrier, I'd prefer that the car break and disintegrate and dissipate all that energy, as opposed to transferring all that energy into me as the occupant.