cars ta ta

[The Natural Philosopher]

Well lets see it. The one near me looks like a large warehouse

[Andrew]

Almost the entire country was on natural gas in the 1960's !!, and most people had switched gas central heating by the 1970's (unless you were a miner getting free coal). Steam trains had gone to Dai Woodhams Barry scrapyard in 1964/5.

According to an article in the DT - "Seventy years ago, there were 2,521,000 cars on the road, compared with

35 million at the end of 2021. Of the 448,000 vehicles produced by the British motor industry in 1952, manufacturers allocated 308,942 units for export. "

Hardly anyone had a private car, and virtually none were diesel. In London you could park your car in Regent street overnight without any issue. Traffic was mostly buses and taxis and it generally flowed freely so you didn't have endless lines of vehicles spewing diesel emissions into your face. Today there are 35 million cars, of which at least a third are diesel and average speeds in London are lower than when there were only 10% of that total.

12 million diesel cars (most pre-EU6), and relentless queues of slow moving or stationary traffic is the fact. 10 times the number of vehicles that were on the road 70 years ago.

Walk along any busy road, especially where there is gradient and cars are joining the main road then accelerating up the gradient and you will see (the smoke) and smell all the pre-EU6 cars and vans.

You have forgotten how bad things have got because you drive everywhere in your Jag with the air-con on, so you simply don't know how bad it is in towns and cities now.

[Andrew]

Without average speed cameras people will just ignore them.

cars run less efficiently as their speed builds up. Driving at a steady 50 will be more economical than driving at 80+.

Some parts of the M4 through Newport are carrying so much traffic that you would be lucky to exceed 50 anyway. This was the inevitable downside of scrapping Severn bridge tolls.

Now those people who have been frozen out of house ownership in Bristol are buying up properties all along the M4 corridor in South Wales and commuting to Bristol instead.

[SteveW]

Certainly.

[The Natural Philosopher]

That entirely depends on the car.

Your simple logic would tell us that a car travelling at 1mph is most efficient of all

Cars have fixed losses and speed dependent losses from aerodynamic drag. The best speed is where they are equal

[The Natural Philosopher]

I have walked in London. Its nothing like as bad as it used to be. You simply cannot conceive of how much difference better car design and catalytic converters have made things.

Diesel buses in particular coated everything in soot.

I was there, then and now. You were not.

[Andrew]

There are no mass produced cars that use less fuel at 80 compared to

50

[The Natural Philosopher]

My cars best speed is around 60.

[alan_m]

That can be the result of road calming and during long periods of the day is so effective in slowing down cars produces grid lock stop/go traffic where the exhaust from vehicles going no-where adds significantly to air pollution.

[alan_m]

Correct, but spending less time in an area may reduce pollution in that area.

[Andrew]

Which is why the pollution is so awful in many cities, too many cars crawling along in stop/start traffic.

Periods when there is a high pressure sitting over the UK makes it worse (sun + humidity + static air + vehicle emissions)

[Ian Jackson]

I may be wrong, but hadn't the fug(g) actually drifted over from The Continent? [Thank heavens that Brexit will stop such things from happening again.]

[Vir Campestris]

Interesting.

I don't have an MPG meter on my car, but my wife's car does.

I've checked it on various sections of roadworks where there's a speed limit. The most recent datum was when I joined the contraflow out of Norwich on the A11 just behind a tractor. I set the cruise to match its speed, and the satnav told me that was 32MPH.

The car reported an average ~95MPG over a reasonably long section of roughly flat road.

That's better than it does at 40 (70-something MPG, I forget the exact number). And that's better than at 50. The slope of the graph is for more economy the slower I go.

And it tells me the most economical speed for the car is slower than I am prepared to drive.

It's a fairly small engine - Hyundai I10 1.3 - so it's possible that another car will give different numbers, but I doubt it's much different.

Why do you think your car is best at 60? Have you done a check at 50?

Andy

[Tim+]

Depends on your definition of “best”. If best means “making reasonable progress whilst saving a bit on fuel” the best speed can be any figure depending on a person’s definition of “reasonable progress” and “saving a bit”.

60 mpg certainly won’t be the most economical speed though.

Tim

[The Natural Philosopher]

Because I have a big 3 liter turbo that uses a lot of fuel just idling. And fairly good aero.

[jon_t]

Just taking delivery of a Polo 2L GTi, after waiting nearly six months. Hope it as refined as the Golf R I have had for the last four years.

[Vir Campestris]

In other words you're guessing.

Ask the trip computer next time you're stuck in a 50 zone, and see what it says.

[The Natural Philosopher]

I do. And in general cruising just below the speed limit gives best mpg

I dont have an instantaneous mpg - only average for the trip

[Vir Campestris]

My wife's little shopping car has an instantaneous reading which is no

*** good at all - all over the shop on the slightest hill. It will also give you a trip average - but you tell it when the "trip" starts by holding a button for a couple of seconds.

What does yours use to determine the start of a trip?

Andy

[Tim Streater]

Starting the car. Mine averages over 10 sec or so periods, much more use for an "instantaneous" reading.