Anyone else noticed this about motorways?

Haych

It's a curiosity I've had for a long time, I don't have an answer.  Was wondering if I'm the only person who notices this and, if anyone else has whether they have an answer.

Not always, but very often I notice that it's quite windy on motorways, yet the trees and other bushes, plants, grasses etc growing on the verges can be virtually motionless.

It also doesn't seem to matter whether there is a lot of traffic or very little to no traffic.

It's like the carriageway has its own weather system almost.

Is there an explanation?

thecolourbox

I'm sure somebody who knows the magical ways of science will have a better answer, but is it something to do with the speed you are travelling relative to the wind perhaps? I don't think i've ever felt a mad side wind in the car whilst in a stationary jam

EricTheWeary

Much of the UK motorway system has embankments on either sides. I am more aware of this when they aren’t there - where it goes past houses on the M50 or there’s a flyover and you see stuff below or motorways in France where you can see across fields. The trees and bushes on either side where they are within those embankments are sheltered to some extent, like a walled garden.You also need very hardy species to survive on the side of a motorway (and other considerations like varieties that doesn’t grow so big they need regular trimming). Any plant that easily bends in the wind probably isn’t going to survive long. 

guitars4you

I've noticed on motorways how many just sit in the middle lane, not overtaking anything and never pull over - As though the inside lane is not for them 

Haych

thecolourbox said:

I'm sure somebody who knows the magical ways of science will have a better answer, but is it something to do with the speed you are travelling relative to the wind perhaps? I don't think i've ever felt a mad side wind in the car whilst in a stationary jam

I'm sure that will have something to do with it, but I never notice the same phenomenon on any other roads, it seems to be unique to motorways, and possibly some stretches of dual carriageway.

AK99

Haych said:

It's a curiosity I've had for a long time, I don't have an answer.  Was wondering if I'm the only person who notices this and, if anyone else has whether they have an answer.

Not always, but very often I notice that it's quite windy on motorways, yet the trees and other bushes, plants, grasses etc growing on the verges can be virtually motionless.

It also doesn't seem to matter whether there is a lot of traffic or very little to no traffic.

It's like the carriageway has its own weather system almost.

Is there an explanation?

Never noticed it per se, but am wondering if whether the effects you are noticing aren't so much down to 'wind' perhaps, but more down to turbulence from other vehicles - or maybe cross-winds at breaks in the embankments, going over bridges/flyovers etc  ?

thecolourbox

guitars4you said:

I've noticed on motorways how many just sit in the middle lane, not overtaking anything and never pull over - As though the inside lane is not for them 

Must be a regional difference, as the motorways I have to go on the inside lane is always full of lorries and Nissans doing 50 with very little opportunity to move over even if I wanted to, and very little point unless you are also only intending on driving at 50

Haych

AK99 said:

Haych said:

It's a curiosity I've had for a long time, I don't have an answer.  Was wondering if I'm the only person who notices this and, if anyone else has whether they have an answer.

Not always, but very often I notice that it's quite windy on motorways, yet the trees and other bushes, plants, grasses etc growing on the verges can be virtually motionless.

It also doesn't seem to matter whether there is a lot of traffic or very little to no traffic.

It's like the carriageway has its own weather system almost.

Is there an explanation?

Never noticed it per se, but am wondering if whether the effects you are noticing aren't so much down to 'wind' perhaps, but more down to turbulence from other vehicles - or maybe cross-winds at breaks in the embankments, going over bridges/flyovers etc  ?

It doesn't seem to matter how much the traffic there is.  Crosswinds do happen as you suggest but I notice often that it's still very gusty on normal stretches of motorway as well.

I do wonder whether eddies of turbulent air move along the carriageway as it's pretty much unrestricted in terms of natural barriers, but maybe I'll never really know.

sev112

guitars4you said:

I've noticed on motorways how many just sit in the middle lane, not overtaking anything and never pull over - As though the inside lane is not for them 

Changed my behaviour since “managed motorways” and on those I won’t sit in the inside lane (there are usually 4) since I saw broken down vehicles in the inside lane without the motorway signals showing it was a closed lane !

AK99

Haych said:

I do wonder whether eddies of turbulent air move along the carriageway as it's pretty much unrestricted in terms of natural barriers, but maybe I'll never really know.

I suspect they may very well do - a single artic moving at 60mph plus is going to leave a fair volume of moving air in its wake trying to fill the shipping sized void of air  behind it (not to mention the combined effects of a whole stream of the things nose-tailing it down the road).

Curious as to how you notice the wind effect btw. I hardly ever notice it in a car, but on some of the bikes it has been pretty noticeable. Worst was the VRod with the nearly solid aluminium front wheel. Every time I went by one of those gates set into a hedge-lined field with even the slightest hint of a cross-wind, the d@mn thing would take a buck leap 3 or 4ft sideways

Adey

thecolourbox said:

guitars4you said:

I've noticed on motorways how many just sit in the middle lane, not overtaking anything and never pull over - As though the inside lane is not for them 

Must be a regional difference, as the motorways I have to go on the inside lane is always full of lorries and Nissans doing 50 with very little opportunity to move over even if I wanted to, and very little point unless you are also only intending on driving at 50

That's me!

It's not safe for me to go faster apparently because I bought budget tyres!

Dominic

guitars4you said:

I've noticed on motorways how many just sit in the middle lane, not overtaking anything and never pull over - As though the inside lane is not for them 

I don't even mind that .......it's when they do it in the outside lane that really bugs me

Danny1969

Most accidents are caused by cars constantly changing lanes. I think the inside lane should be for the 50 to 60 brigade, middle lane for 75 max  law abiders and the outer lane left to the speeders. 

sev112

But that’s a bit like saying people that drown at sea were in a boat, therefore let’s legislate against boats.

i guess if your stat is true (possible) then it’s inappropriate driving (while changing lanes) rather than changing lanes causing accidents 

Danny1969

sev112 said:

But that’s a bit like saying people that drown at sea were in a boat, therefore let’s legislate against boats.

i guess if your stat is true (possible) then it’s inappropriate driving (while changing lanes) rather than changing lanes causing accidents 

I think it's things like blind spots in mirrors, loss of traction in bad weather, cars changing from outer lane to middle at the same time and spot a car is changing from inner lane to middle. I think if  you stick to one lane and keep a safe distance from the car in front it's very unlikely you will be in an accident. 

I don't like driving myself and hate cars so just keep left anyway. I sometimes wonder if everyone is meant to keep in the inner lane and keep darting out to overtake and then dart back in ? ... seems crazy to me 

Devil#20

guitars4you said:

I've noticed on motorways how many just sit in the middle lane, not overtaking anything and never pull over - As though the inside lane is not for them 

This is particularly annoying. Unless you undertake then they are effectively reducing motorway capacity by a third. Also if you have a blowout in the outer lane you have nowhere else to go. The middle and outer lane are for overtaking only. I don't think a lot of drivers realise that. 

blobb

There's a sewage analogy to do with motorways (you wil be pleased to hear). 

The movement of traffic is directly comparable to dynamics of particular settlement in a settlement tank. You have to imagine the lanes stood upright for it to work with traffic 'falling' to the bottom.

 When traffic is free flowing the 'particles' can flow at their own individual rate, they are completely dispersed, there is no physical contact and the concentration is too disperse for them to influence each others behaviour. The particles move at their own rate governed by their size, porosity and density or, in the case of motorists, their driving habits, horsepower and possibly penis size.  

As the solids (traffic) concentration increases beyond a certain threshold they begin to interact with each other and the particles no longer settle independantly, creating what is known as a zone of hindered settlement. in this zone inter-particle forces are sufficiently strong to drag other particles along at the same velocity irrespective of size, density, social status and phallic bragging rights. The particles settle collectively as a zone (zone settlement). 

Above a critical concentration, the zone transitions to compression settlement where, if you are not careful, this can lead to physical interaction between the particles, comonly known in motoring parlance as a 'pile up'. The settlement velocity here is obviously much lower than in the hindered settlement phase. 

This is the theory behind variable speed limits on so called 'managed' motorways. It maintains the hindered settlement phase before it becomes compression. The optimium rate of settlement is called the Vesilind velocity. If you have roadworks or a broken down car blocking a lane (a bottleneck in the underflow or removal rate from the tank) you make things worse.  Analysis of particular settlement and comparison with removal via the underflow route is called Mass Flux theory.

This is how activated sludge sewage plants work.

Don't say we never learn you anything (and yes, I'm fun at parties).

AK99

^ Used to dread fluid-dynamics at college..but solid(s)-dynamics..now there's a thing..

Devil#20

AK99 said:

^ Used to dread fluid-dynamics at college..but solid(s)-dynamics..now there's a thing..

It's an inexact science anyway. It was hoped that millions could be saved on running wind tunnels and model it with computational fluid dynamics and Navier Stokes equations but comparison of results has never been sufficiently close to rely solely on it for aircraft design (or at least not for military fighter aircraft). Good for predicting macro or incremental effects, so it does supplement or support wind tunnel results at some level but isn't a viable alternative replacement.  

AK99

^ Great for tormenting the 'jz-but-I-hate-bstrdin-maths' types like me though..

snowblind

WRT the original post I suspect the trees appearing motionless is actually some kind of optical illusion caused by the motion of the car relative to the "stationary" trees. Think of it in terms of like when you see a plane flying over when you are in a moving vehicle and the plane appears to be motionless. It a glorified parallax effect.

There may also be an element of visual processing at work as your brain interprets conflicting signals. Your are sat motionless inside a moving frame of reference viewing supposedly stationary points of interest which are actually also moving. It is a scenario we won't have evolved to deal with so likely it is just your brain making the best of what its got.

Ever done that thing where you are sat in the back of a moving vehicle look out behind you for any length of time? When the vehicle stops the world appears to continue moving away from you due your brain having been trying to compensate for the movement relative to your seated position. 
Similarly those glasses that invert your view which your brain then adapts to making the world appear the right way up. Until you take the glasses off of course.

Addendum: These compensatory effects in the brain are why VR is never going to be a great success for most people. If you've ever spent more than about 15 minutes in VR you will probably have noticed the brief sense of disorientation when you exit as your brain remaps itself to reality. Extend the VR immersion to a few hours and that disorientation won't be quite so brief.