Increasing car size and road congestion? - daiking
I looked for studies/research in this area but haven't found anything. Does anyone know of any evidence or figures to support this? The gist is basically this:

It is commonly known that cars in the same category have got bigger over the past few years. For example, a 1980s Ford Escort hatchback was 4.013m long while a Focus II, Ford's current class competitor is 4.342m long (nearly 13" longer for the old timers ;-) ). Similarly an 80s Sierra hatchback was 4.419m long and the equivalent mondeo today is 4.731m long, an increase of approx. 12". (Figures unscientifically gathered from Parkers)

So presumably even if there were the same total number of cars on the road as there were 20 years ago, the increased size of modern cars would take up more road space and result in 'congestion'. Given that there are also many bigger cars on today's road - MPV and 4x4s than there were 20 years ago and there are actually more vehicles anyway. What effect on congestion can be attributed to bigger vehicles, not just more vehicles?

Do wake up at the back!

Increasing car size and road congestion? - Vin {P}
Except that if you're driving on, say a motorway at 70mph, the minimum recommended distance between cars is 2 seconds = 210ft. In which case an extra foot or two n the car itself is pretty much irrelevant.

It would have some effect at slower speeds, and must make the jams longer for the same number of cars..

V
Increasing car size and road congestion? - jase1
There probably is a slight effect, but it shouldn't be that much. In a 30mph zone you should be at least two, if not four "car lengths" from the car in front -- so the effect of an increased car size is divided by 5 if we assume 4 car lengths (and assuming that the notion of a "car length" for the purposes of gauging distance from the car in front doesn't change).

So an increase of a foot on a car that is 13ft long is only effectively around 1.5% (1/5th of 1/13th).

That 1.5% is pretty significant, but it's not as huge as you'd at first think.
Increasing car size and road congestion? - daiking
>>In a 30mph zone you should be at least two,
if not four "car lengths" from the car in front


LOL, I see plenty of motorway driving at less than those clearances! I was thinking of urban congestion rather than motorways (in response to first reply). IMO I'd think that there are more bigger cars around nowadays so the actual average size would be a couple of feet longer. But that's only my perception, could be totally wrong. As you say, driving distances and overall behaviour could negate the effect of fatter cars. That's why I was looking for some statistical model to back up any claims. Similarly, how has road haulage increased since the mid 80s and does the size of these vehicles unduly increase congestion compared to the nominal increase in numbers of HGVs?
Increasing car size and road congestion? - Waino
Similarly, how has road haulage increased since the mid 80s and does
the size of these vehicles unduly increase congestion compared to the
nominal increase in numbers of HGVs?


Although HGVs are longer, the drivers make up for it by driving very close to the vehicle in front.
Increasing car size and road congestion? - P3t3r
I agree with what other people are saying. I think the size of the car is negligible compared to the gap between cars when their when the speed is over 20mph. I do not like the width of cars though when you bear in mind that garages and parking spaces are not getting bigger. I have a small car, and park very carefully in the hope that fewer idiots will knock my car. Unfortunately , even when they have loads of room they still manage to dent my car :(. I also find small cars make it much easier to do DIY servicing/repairs in a garage.
Increasing car size and road congestion? - daiking
Small parking spaces is another one of these obese car problems. Personally I think people understate the bigger car effect as the congestion I get stuck in is city centre, stop/start driving with frustratingly sequenced traffic lights. When stationary, the increased length is proportionally greater. What about how a slight overload can affect the overall system far more than the proportional increase in flow? Has no one ever seen any work looking at this? Where can you find reliable figures concerning current and historic congestion levels?
Increasing car size and road congestion? - Bromptonaut
Agree with p3t3r, it's the width and bulk of cars that are at issue rather than the length. Face to face in the high street with a Dodge Ram the other day, slowed me a lot more than similar off set with another Berlingo!!
Increasing car size and road congestion? - jase1
This is a potential problem with MPVs and 4x4s if you think about it.

To be safe, you need to be further away from these vehicles to be able to see around them, than ordinary-sized ones.

This isn't an issue on the motorway if you're complying with the two-second rule, but it becomes a problem in urban/30mph traffic.

So yes, the bulk of modern vehicles is far more of a problem than length -- and in the race to bigger and bigger vehicles, it's only going to get worse, with people insisting on buying 5-seat MPVs for the perceived benefit of extra cubby-holes etc.

It's an interesting topic though.
Increasing car size and road congestion? - mk124
Agree that this is an intresting topic. One factor people have seemed to miss out at motorway speeds is that cars are much safer (and therefore longer?) than before. Some people on this forum have questions the use of safer cars. In their mind safer cars will encourage less safe driving. On a motorway this may mean more tailgaiting.

To apply what this means for superminis on the motorway we can think as thus. A typical supermini in 1996 will be about 3.8 meters long and leaves a gap of about 70 meters from the car infront at 70 mph. This makes a grand total of 73.8 meters.
In our new 5 Ncap star superminis of about 4 meters in length lets assume the average driver leaves a gap of about 63 meters from the car infront at 70 mph. This makes a grand total of 67 meters.
My hypothesis is that safer cars (safer for the driver) are often longer and thus the englargment of cars through the years will reduce conjestion on the motorway, rather than increase it as some posters have implied. That is car length is not independent of driving style.

(sorry OP asked about urban conjestion)
Increasing car size and road congestion? - Westpig
I also find small cars make it much easier to do DIY servicing/repairs in a
garage.

you're not wrong, both my car and my wife's will not physically fit in my garage. Hers with both the mirrors in will go in the door gap, but is then too long......... mine, even with the mirrors in will only fit with about an inch to spare either side and of course without the use of the mirrors you can't judge it very well to get back out.

my mk1 Triumph 2000 fits in a piece of cake...and that wasn't a small car in its' time.........you'd think house builders would have sussed this by now wouldn't you
Increasing car size and road congestion? - L'escargot
>>........you'd think house builders would
have sussed this by now wouldn't you


I think they work on the assumption that most people use their garage for storing junk and not for putting their car in.
--
L\'escargot.
Increasing car size and road congestion? - turbo11
I think they work on the assumption that most people
use their garage for storing junk and not for putting their
car in.

Yes.,heard that a recent survey by the AA (i think) showed that only 1 in 5 people wlth garages actually keep their cars in it.My car definately will not fit in my garage, even without all my stuff stored inside.
Increasing car size and road congestion? - teabelly
There's also an added complication. At slower speeds the gaps are smaller but each journey will take longer and therefore more cars will be on the road at the same time. This also adds to the congestion as there are more vehicles on the road at once. Everyone has noticed how there seem to be more cars on the road and yet actual BVKM fell in 2005 and yet most people's experiences on here are how congested everywhere is and how much longer it takes to get anywhere.

House builders are cheap skates which is why garages are too small and so is the rest of the house :-)
teabelly
Increasing car size and road congestion? - Dulwich Estate
The significant reason for "in-town" congestion getting worse recently (10 -15 years) is the now universal one-man operated bus with doors. They are stationary at bus stops just so much longer than they used to be and we all sit patiently behind them. It might save the transport co. a few bob but it costs the wider community so much more. Rant over.
Increasing car size and road congestion? - alex

In-town congestion has also got worse through local councils' "traffic calming" measures.

What happens is that the Council might narrow road so that, for example, only one car can queue to join a junction/roadabout whereas before there would have been space for two vehicles abreast.

But the increased width of modern cars hasn't helped as on narrow roads a car might be too wide to pass to the left of a vehicle wanting to turn right.
Increasing car size and road congestion? - madf
I forget my queuing theory but I am sure - by definition - longer cars = bigger queues.

But a small impact.. the problem is just more cars...

And the UK population is rising .. now over 60 million.

Anyone see the connection?

Nope...thought not:-)))
madf
Increasing car size and road congestion? - jase1
The significant reason for "in-town" congestion getting worse recently (10 -15
years) is the now universal one-man operated bus with doors. They
are stationary at bus stops just so much longer than they
used to be and we all sit patiently behind them. It
might save the transport co. a few bob but it costs
the wider community so much more. Rant over.


That is such a good point, I never thought of that. You're absolutely right. It's more than 10-15 years though, the last time I saw a bus conductor round these parts was when I was a small child in the 1970s....
 

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