Is this bad behavior from lorry drivers?

dil1976

sevenhills said:

prowla said:

55 on a motorway is obstructive and bad manners.

Driving at 55 on a motorway would be a fail in a car, you should set your speed to the road conditions, not your MPG.

What exactly would they fail?

dil1976

Everyone saying driving at 55 is dangerous, do you realise most hgvs are limited to a speed just over that? Does that make them dangerous too?

Car_54

sevenhills said:

prowla said:

55 on a motorway is obstructive and bad manners.

Driving at 55 on a motorway would be a fail in a car, you should set your speed to the road conditions, not your MPG.

It would if the test included motorways, which it doesn't.

jb66

55mph is a really irritating speed for lorry drivers, some lorries are limited to 56-60mph so it means they have to unnecessarily pull out into the overtaking lane to overtake you at 1mph.  I would recommend setting cruise control to 62mph that way your slightly faster than lorries and wont encounter this issue

sevenhills

Highway code rule 146, adapt your driving appropriate for the road and conditions.

[Deleted User]

I think you need to look at the bigger picture instead of just focusing on your mpg at the expense of everyone else, a few mph more might not cost you anything but will make the roads easier and more pleasant for everyone else.

If you want to save fuel and travel around the speed of the lorries, adjust your speed to match the flow of the traffic. You might actually find that your car is rather optimal fuel-wise at 56mph (your speedo will show around 59-62mph) as that is one of the tested speeds for official fuel consumption figures so likely that manufacturers have a sweet spot in terms of gearing and engine tuning around the 56mph point.

You will also then not be slower than the fastest lorries running on the 56mph limiter unless they are going downhill, in which case they can overrun the limiter and quite legally do up to 60 mph - equally adjust to keep up with lorries on downhills to avoid them braking for you.

Bear in mind:

1. Your indicated 55mph on the speedo is probably around 49-52mph true speed. Who said this is the most economical speed in your car?

2. It is incredibly frustrating for lorry drivers to sit behind a vehicle that stops them from utilising all their speed up to the limiter which can be anything from 52 up to 56mph max. They are allowed to do 60mph so they are already penalised by the limiter, and now you are shaving a few mph of that.

3. To overtake you they will clog up the 2nd lane at 52-56mph and probably take a long distance to do that, causing congestion for everyone. Somebody doing 60 mph because just like you they stubbornly feel like it now moves into 3rd lane to slowly overtake and the whole speed of the motorway drops.

4. If a lorry slows down because they can't overtake you, it is hard work and extra fuel for them to get back up to speed to overtake. They will struggle to find a gap in busy traffic conditions to overtake and on 2 lane dual carriageways will clog the outer lane.

5. Transport costs are a significant part of the good we purchase every day, have some consideration of that and how that impacts you if you are causing delays to lorries or for them to use more fuel.

sevenhills

[Deleted User] said:

It would if the test included motorways, which it doesn't.

It would certainly be a negative on a 70 mph dual carriageway.

Alanp

I thought driving at 55mph was the fuel saving method back in the 70s, not sure if with todays modern engines/fuel systems would save much fuel than if you were travelling at motorway speeds, I went down to Cornwall this year, cruise set to 70mph, and was averaging 57mpg according to the trip ( yes I know this isn’t the way to calculate true mpg)

[Deleted User]

Alanp said:

I thought driving at 55mph was the fuel saving method back in the 70s, not sure if with todays modern engines/fuel systems would save much fuel than if you were travelling at motorway speeds, I went down to Cornwall this year, cruise set to 70mph, and was averaging 57mpg according to the trip ( yes I know this isn’t the way to calculate true mpg)

Physics hasn't changed since the 70's.

Aerodynamic drag is proportional to the square of the object's speed. In basic terms, when speed doubles, wind resistance quadruples.

So faster speeds will always need more energy to travel the same distance, but factoring in things like the aerodynamics, weight, engine, gear ratios, fuel type etc will all result in a different optimum speed for fuel consumption.

Taking away wind resistance completely, cars will have a particular engine speed that is most efficient, that might be some point in the 1500-3000 rpm typically, combine that with the highest gear in the gearbox and that is the most economical speed. Add back in wind resistance and a new most economical speed will prevail as it may work out more economical to run at less efficient revs but with much lower wind resistance.

Some aerodynamic sports-type cars might see their most economical speeds being at 70 - 80 mph for example due to a lesser effect of wind resistance and gearing favouring higher speeds resulting in the engine running at more efficient revs at higher speeds.

Typically EV's are nearer 40 mph for the most economical speed as the wind factor is the main element as gearing doesn't come into play and the motors have similar efficiency across the rev range.






 

Alanp

I guess wind resistance, weight, and aerodynamics count for nothing if the op is rear ended by a 30 tonner because he’s driving like a Richard.