Motorway Driving and Micro-Skidding?

Ostrom

As best I can describe it!

Have had my license a week now and took my car (04 Fiesta) on the motorway last Saturday, and again last Tuesday. The car does a comfortable 120, although I prefer to keep left and do around 100.

I have noticed the car seems to pull slightly and suddenly to the front at high speeds - the best I can describe it is like a minute skid that edges the car slightly in either direction. I can feel the wind swaying the car at higher speeds, particularly on open stretches of road.

I have no experience of motorway-speed driving. Is this normal?

My tread depth is fine, the car doesn't pull on the straight so I'm fairly sure my alignment is ok (there isnt any wear on any particular portion of the tyre either). It was particularly bad driving home in the snow on Tuesday, even though I was keeping my speed well below the limit.

I'm a little nervous about taking it down the M4 tomorrow.....

php-fox

From my point of view it is fine, especially in windy weather and with the small lightweight car.
I drive mazda 3 which is relatively big and heavy. But a few weeks ago I rented an opel corsa while in England. I could feel the car almost "jumping" up on the motorway if a truck passed me by.

So, my advice keep the car straight, closer to middle of the lane and don't panic.

DriveSkill

From what you describe it is most likely just effects of crosswinds or overtaking traffic (especially large trucks, buses etc). Some stretches of road are more prone to it than others and at higher speed with a small/light cars it will be noticeable. Be aware of overtaking traffic and also of warning signs for areas prone to crosswinds - in these circumstances you need to keep a slightly firmer grip on the steering wheel and maintain your position on the road.

One important safety point about driving on Motorways is that you do not want to be driving too slow. 90-100 km/hr is about as slow as you should go (assuming of course traffic is moving freely and road/weather conditions are good!). If you are driving too slow for the road conditions most traffic will end up overtaking you which is actually more dangerous than keeping with the flow. You also run the risk of someone appoaching behind at 120km/hr and not noticing you until its too late!

daveharnett

+1 on what driveskill said - it's normal for cars to get a little "floaty" at speed (what speed that is depends on the weight and aerodynamics). A fiesta starting to feel light at 120 wouldn't surprise me - it's not designed to cruise at that pace.

If what you are describing is more pronounced than a slight tenancy to drift, have somebody take a quick look at the front suspension - failed bushings can allow the wheels to shift around a little, even when driving in a straight line. From your description, it sounds like it's normal though.

Wishbone Ash

DriveSkill wrote: »

. 90-100 km/hr is about as slow as you should go (assuming of course traffic is moving freely and road/weather conditions are good!). If you are driving too slow for the road conditions most traffic will end up overtaking you which is actually more dangerous than keeping with the flow. You also run the risk of someone appoaching behind at 120km/hr and not noticing you until its too late!

Some categories of vehicles are legally limited to 65kph and 80kph regardless of the posted speed limit. I take the point you are making but I don't think someone should have to drive up to a particular speed to accomodate inattentive drivers.

DriveSkill

Wishbone Ash wrote: »

Some categories of vehicles are legally limited to 65kph and 80kph regardless of the posted speed limit. I take the point you are making but I don't think someone should have to drive up to a particular speed to accomodate inattentive drivers.

True, although not sure if buses restricted to 65 km/hr use the motorways - maybe someone could confirm. To be honest I dont see many of trucks and buses complying to the 80 km/hr limit!

I guess the point I was trying to make is on a freeflowing motorway where the vast majority of traffic is travelling at or near the speed limit of 120 km/hr it can be dangerous to be driving significantly slower - especially in a car as people will expect a bus/truck to be going slower. We dont have it in Ireland but in a lot of other countries there is a minimum as well as a maximum speed limit on motorways for this very reason.

If a driver feels uncomfortable driving at higher speed then the best advice would be to build up some experience at quiet times on the motorway and if necessary use the National routes in busier times until you feel more confident. You dont want to be in a position where you feel pressured into driving a higher speed than you are confident with so I hope my initial post didnt imply that - that wasnt the intention.

Wishbone Ash

DriveSkill wrote: »

True, although not sure if buses restricted to 65 km/hr use the motorways - maybe someone could confirm

Double deck buses and buses with standing passengers are limited to 65kph and may use motorways (e.g. Dublin Bus airport shuttles 747, 748 etc.)

DriveSkill wrote:

there is a minimum as well as a maximum speed limit on motorways for this very reason

How do they enforce a minimum limit? Who determines the boundry between free flowing and non-free flowing?

DriveSkill wrote:

If a driver feels uncomfortable driving at higher speed then the best advice would be to build up some experience at quiet times on the motorway and if necessary use the National routes in busier times until you feel more confident. You dont want to be in a position where you feel pressured into driving a higher speed than you are confident with so I hope my initial post didnt imply that - that wasnt the intention.

I been driving for many years in all categories of vehicles but I occasionally find traffic on motoways travelling at a speed that I don't find confortable with the prevailing conditions. An example is when it is very wet, foggy or several degrees below zero at 4 or 5am with a danger of black ice and many drivers continue at 120kph!

DriveSkill

Wishbone Ash wrote: »

How do they enforce a minimum limit? Who determines the boundry between free flowing and non-free flowing?

Not sure how they enforce it to be honest - I guess its more common sense in that if there is a congested motorway then you cant enforce but if is one driver slowing everything down then you can certainly enforce it. Its not done via auto speed cameras as far as I know - more likely to be patrol cars.

The law exists in Portugal and I believe in the Netherlands (but its been a while since I drove there). It is also used in parts of the US (Florida as far as I remember at least). Granted the minimum speed limit is pretty low (around 50-60km/hr) and in some cases varies by lane so the overtaking lane will have a higher minimum etc.

Wishbone Ash wrote: »

I been driving for many years in all categories of vehicles but I occasionally find traffic on motoways travelling at a speed that I don't find confortable with the prevailing conditions. An example is when it is very wet, foggy or several degrees below zero at 4 or 5am with a danger of black ice and many drivers continue at 120kph!

Totally agree with you. In Ireland we take the view that 'one size fits all' or maybe that should be 'one speed limit suits always' For example in France the speed limit reduces when its raining - I think it drops from 130km/hr to 110km/hr for Motorways.

The important point to remember is the safe speed at which you can travel can vary significantly depending on a number of factors - weather, time of day, traffic etc so it might be "safe" to travel at 130kph on a bright summers night with no traffic but the same stretch of road could be lethal even at 70-80kph on a dark, foggy, cold evening etc. Unfortunately a lot of drivers appears to only look at the speed limit signs (if they even do that ) and disregard all the other factors.