[Nick]

Not the sort that a bit of Vicks Vaporub can sort out for you!
The sort that leaves you sat in your car waiting at roadworks for ages, or just sheer volume of traffic on a too small road.

This recent article talks through the latest report from INRIX - a global transportation analytics company - and reveals the UK's top cities for congestion, where drivers spend the most time sat in traffic, and how much it costs per driver.

The top 5?
1. London
2. Bristol
3. Leeds
4. Manchester
5. Bath

Check out the article for the rest, including the most congested cities in Europe and Globally.

Question to you all - how are you affected by congestion? Do you live in any of the cities listed and can identify? Let us know your thoughts.

[Rolebama]

I live in outer suburbs of NW London, and congestion is rampant. Some relatively short journeys of 3 to 5 miles, at the wrong time of day, can take up to 40mins. I travel clockwise on the M25 occasionally, at 6am. I can travel in very light traffic, but the anti-clock carriageway is near stationary for miles. This can have a knock-on effect for miles around me. A particular hate is if I have to use any of the local dual carriageways on a journey. Congestion is very erratic outside of rush hours and school run times. I do most of my driving late night or very early morning.
Personal conspiracy theory is that most of the traffic lights and roundabouts are set up to waste as much fuel as possible, counter-intuitive as it may sound, I find traffic flows better when traffic lights fail.

[Drivingforfun]

I'm not sure if any mechanically-minded people can answer, but is the relationship between fuel consumption & emissions linear? (i.e. if a car uses 50% more fuel does it produce 50% more emissions?)

I don't know if that's a stupid question or not ... as, going by the stats, a Fiesta products half the emissions of a GT86, but does well under double the mpg, but we all know the "on paper" figures are quite fantasy

It does seem there's a huge conflict of interest when the govt. has as much an incentive as disincentive to have us burn as much fuel as possible??

[Nick]

So I'm definitely not mechanically-minded @Drivingforfun , but I'm going to stick my neck out and suggest that yes, it's essentially linear. I'm struggling to find any direct evidence to support this through a Google search, but the chart at this link makes me think yes 0 and i accept that it's purely there for illustrative purposes but it makes sense to me. Would love to hear others thoughts.

We've had some recent congestion through my small-ish town recently following some changes to traffic lights and the perceived increase in air pollution from exhausts of cars stood waiting has come up often through the usual local forums online.

https://www.wltpfacts.eu/link-betwee...l-consumption/

[Beelzebub]

Never mind mechanics, I'm relying on Physics and Chemistry lessons from 100 years ago ...

I can see no reason why it would NOT be linear. One litre of fuel will always produce x ml of CO2, y of CO, z of NOX, etc.

Bur someone who left school more recently may have a different answer!

[olduser]

This is where a diesel wins over petrol.
At tick-over a diesel just has less fuel injected just enough to keep it turning over.
But a petrol engine is starved of air (by closing the throttle) making the engine have to work harder to breath, this drops the (effective) compression ratio making it less efficient, and the mixture is made slightly richer.

A bigger engine will need more fuel to turn it over.

Some NOX is a product of compressing and heating air, a diesel engine then will produce NOX even if it is not burning fuel just like an air compressor does, a petrol less so as the compression ratio is usually lower.

Of course standing still the engine consumes fuel for no benefit, hence the fashion for auto stop/start.
But that opens another can of worms - electric motors just smile and cool down a bit.

[olduser]

Congestion is the natural endpoint of mass car ownership and use.

Hopefully, given sufficient congestion, people will consider other ways of getting there but a car is probably the second most expensive thing we will ever buy so we will sit in the car for hours in congestion because having spent all that money to buy, tax, and insure it it would be stupid to leave it at home!?

Sitting in congestion reduces the likelihood of crashing and injuring someone or getting caught speeding!

[Rolebama]

There are other factors involved as well which will 'waste' fuel when idling. The increased richness of petrol is caused by the power necessary required to keep the engine running as it does not have the kinetic energy of running faster to help. Couple this with alternator loading to run heating/cooling, lights, hrw, all the computer bits and pieces, and in too many cases brake lights, all loading the engine, the requirement for the extra power required are met by increased fuel usage. Bearing in mind that our rush hours run into periods of darkness for quite a period of the year.
Things like auto-start and on/off charging systems were only introduced to aid in the govt emission test, and have no use in the 'real' world. When was the last time you saw a petrol car with the engine off in congestion during rush hour when it was cold or wet or dark or any combination?

[olduser]

Last time I drove my Ford Fiesta, the taxis used by my hospital transport all turn the engine off as soon as they stop.
I must admit, it was a bit unnerving when I first drove a car with that fitted.

[NMNeil]

Rush hour where I live 😉

[Nick]

Originally Posted by olduser

Last time I drove my Ford Fiesta, the taxis used by my hospital transport all turn the engine off as soon as they stop.
I must admit, it was a bit unnerving when I first drove a car with that fitted.

My Grandland has Stop/Start fitted as well and i definitely spooked me for the first few times. Having said that, for some reason it never seems to kick in any longer - I believe it's something to do with whatever else is going on in the car, ambient temperature not right or something! It would be better if it just did it regardless.

[olduser]

Originally Posted by Nick

My Grandland has Stop/Start fitted as well and i definitely spooked me for the first few times. Having said that, for some reason it never seems to kick in any longer - I believe it's something to do with whatever else is going on in the car, ambient temperature not right or something! It would be better if it just did it regardless.

It will not stop the engine if it is not warmed up or battery charge too low, aircon on/ heating on and car cold, gear in neutral or park, and I think on some cars the engine stop can be turned off.
The software designer has tried to think of all situations where it just would not make sense to turn the engine off.

[Rolebama]

@NMNeil I have never seen traffic that light in daytime! I think the lightest I ever saw was leaving Kilmarnock at 07.30am, but even then there was more than that around.

Mine has auto start, and it did take some getting used to. It is possible to turn it off, although I leave it on. This is because reverse gear is a bit high, and I do still occasionally stall when reversing up a gradient. (I really hate having to slip the clutch.) Just completely disengaging the clutch restarts it.

[NMNeil]

Originally Posted by Rolebama

@NMNeil I have never seen traffic that light in daytime! I think the lightest I ever saw was leaving Kilmarnock at 07.30am, but even then there was more than that around.

When I first moved to LA I was amazed at how cheap petrol was, how clean the air was and how there was so little congestion, but after 6 months or so I was with everyone else moaning about the high cost of petrol, the pollution and the traffic congestion, so it's all relative. 😂