What is the "Correct" Speed Limit?

[kasdashd]

There's a trend towards lower speed limits in cities all over the world, but why is this happening? What is the research behind it? And what is the "correct" speed limit for cities, anyway?

 

 

[Lurking]

They do that here (Madison, WI) to make the 4 or 6 lane highways all be 25 mph zones. Regular 2 lane side streets still have the 35 or whatever limit.

 

Lots of people pulled over and ticketed since those highways are built for high speed. That also answers the question why they do it ...

 

They say it is for safety. But almost no actual infrastructure improvements are provided. 

 

There is a way to design roads for low and high speed and use the 85th percentile if drivers to set the posted speed limit. All those rules are thrown out for ticket revenue 

[Monkey Dust]

There are an increasing number of 20 mph (32 kph) limits in the UK. Honestly, I think it causes people to just pay less attention to driving. That said, in the Bristol rush hour, 20 mph is often an impossible dream.

 

The point about heavier vehicles is valid, a 2500Kg car is bringing double the energy to an accident as a 1250kg one at the same speed. And there are a lot more 2500kg cars about, even in Europe. Differential speed limits for different car weights would be too complicated to implement, so it sadly makes sense to lower the limits for everyone.

[Lurking]

23 minutes ago, Monkey Dust said:

There are an increasing number of 20 mph (32 kph) limits in the UK. Honestly, I think it causes people to just pay less attention to driving. That said, in the Bristol rush hour, 20 mph is often an impossible dream.

 

The point about heavier vehicles is valid, a 2500Kg car is bringing double the energy to an accident as a 1250kg one at the same speed. And there are a lot more 2500kg cars about, even in Europe. Differential speed limits for different car weights would be too complicated to implement, so it sadly makes sense to lower the limits for everyone.

Different speeds are dangerous. Imagine a highway and everyone driving the same speed will be safe since there is no passing, lane changing, braking etc. necessary. Now the same highway with people driving from 50 to 70 mph. Now you have people going around other people, having to slow and accelerate, going into blind spots etc. Much more dangerous. And drivers will be very stressed and tense.

[Monkey Dust]

1 hour ago, Lurking said:

Different speeds are dangerous. Imagine a highway and everyone driving the same speed will be safe since there is no passing, lane changing, braking etc. necessary. Now the same highway with people driving from 50 to 70 mph. Now you have people going around other people, having to slow and accelerate, going into blind spots etc. Much more dangerous. And drivers will be very stressed and tense.

In the UK, and I think the whole of the EU, we have different speed limits for different vehicles. Heavy goods vehicles and buses are limited to 90 kph/56mph. On 70mph roads, large vans and anyone towing is limited to 60mph. People will almost always be travelling at different speeds on a multi-lane road. I don't know about the US, but in the UK, the motorways (what we call highways) are the safest roads in the country, despite high speed differentials between vehicles.

[vf1000ride]

My speed limit depends on the capabilities of the vehicle I am driving and the road/weather conditions and less to do with the posted signs. My truck I am closer to the posted limit, maybe 10 over.  The sports car is consistently over by 15-20mph.  My motorcycles are anywhere from 10 over to ohhh dang that might have not been safe.  

 

In my area of the US the speed limits vary greatly depending on what local, city, state roads and are not consistent as each small town is allowed to set their own speeds.  Major highways are usually the most consistent either 65-70mph some have truck restrictions, some don't.  Smaller surface roads outside the city/towns are usually anywhere from 25-55mph.  In cities and towns they are usually 25-35mph.  

[Godlygamer23]

9 hours ago, Lurking said:

Different speeds are dangerous. Imagine a highway and everyone driving the same speed will be safe since there is no passing, lane changing, braking etc. necessary. Now the same highway with people driving from 50 to 70 mph. Now you have people going around other people, having to slow and accelerate, going into blind spots etc. Much more dangerous. And drivers will be very stressed and tense.

Not sure where you drive, but this is already a thing on the highway essentially in my area(East Coast), because people drive different speeds, based on whether or not it's a company vehicle(speed monitored), what they're comfortable with, etc. Most people in my area are doing 80-90 in a 65MPH zone in both lanes, so any difference in speed forces people to move over, and then back again.

 

So implementing it based on vehicle size, and gross weight is just taking it another step forward. Rigs and other vehicles carrying heavy items(or carrying them in a more precarious way) may naturally drive at a lower rate anyway.

[Blasty Blosty]

On 5/6/2024 at 5:06 PM, Monkey Dust said:

There are an increasing number of 20 mph (32 kph) limits in the UK. Honestly, I think it causes people to just pay less attention to driving

I hated them when I was learning to drive, as everyone wants to overtake me. To me it just creates a dangerous and toxic interaction between legal drivers and speeders.

[Monkey Dust]

17 hours ago, Phantasmagoria said:

 

 

Doing that without the engine fully up to temperature, I feel that engine's pain. If the water isn't up to temp, as in this vid, the oil will be nowhere near. I'm all for driving a car like you stole it when it's warmed up properly, but until it is, you should treat it gently. 

[Needfuldoer]

45 minutes ago, Monkey Dust said:

Doing that without the engine fully up to temperature, I feel that engine's pain. If the water isn't up to temp, as in this vid, the oil will be nowhere near. I'm all for driving a car like you stole it when it's warmed up properly, but until it is, you should treat it gently. 

Looks like it's around 220, if the gauge is accurate.

 

[Kid.Lazer]

On 5/6/2024 at 12:26 PM, Lurking said:

Different speeds are dangerous. Imagine a highway and everyone driving the same speed will be safe since there is no passing, lane changing, braking etc. necessary. Now the same highway with people driving from 50 to 70 mph. Now you have people going around other people, having to slow and accelerate, going into blind spots etc. Much more dangerous. And drivers will be very stressed and tense.

That description is Pennsylvania highways. We have quite a few roads like I-81 where the speed limit can fluctuate through the mountains. And of course, the cops LOVE to sit right at the sign boundaries to pull over people that didn't slow down!

[Monkey Dust]

55 minutes ago, Needfuldoer said:

Looks like it's around 220, if the gauge is accurate.

 

The needle isn't pointing at, or near, the centre, which for most cars is the engine's normal operating temperature. Also, unless I'm miss remembering (and it has been many years since I've driven an M BMW) the amber lights on tacho gradually go out as the engine warms up, until there are none left. There is still one amber light left illuminated, so it isn't fully warmed up.