How To Drive Safely In Wet Weather

How To Drive Safely In Wet Weather

The golden rule for safer driving in wet weather that is continually broadcast by safety organisations is to SLOW DOWN and allow more space between yourself and other road users!  So why is it that so many people are blissfully ignorant of the importance of this advice and continue to rush from point A to point B, right up the back of the car in front?
 
Is it because the message becomes lost in the background noise of the modern day hustle and bustle of life or is it because the importance and comprehension of why the rule should apply is not fully understood?  Possibly it's a combination of both.
 
To help comprehension and hopefully make the advice the golden rule for all road users, the following explanation provides some of the background mechanics and physics of what keeps a car on the road and how to avoid collisions with other road users especially when driving in wet weather.


Vehicle Control

Despite significant advances in automobile safety technology the fact remains that the four contact areas between the tyre and the road surface (with the resultant coefficient of friction (grip)) are the only means through which the driver can affect vehicle control. Tyre grip is the ultimate limiting factor for braking and directional control; click here for more information on tyre performance. 
 
Modern motor vehicle safety technologies (http://www.subaru.com.au/car-advice/safety) such as ABS braking, electronic stability control, All Wheel Drive (http://www.subaru.com.au/car-advice/awd-vs-rwd), vehicle chassis and suspension design help to maximise the available tyre grip but if there is no tyre grip due to road conditions, no control is possible.  So in wet weather when the grip between tyre and road surface is significantly reduced, as a result of a lower coefficient of friction, the ability of the driver to control the vehicle is also significantly lower.  Most drivers would understand that in wet weather the road surface is slippery but they fail to fully comprehend the magnitude of the effect that wet weather combined with vehicle speed has on vehicle control.


Braking Distance

What is not generally understood is that higher vehicle speed exponentially increases vehicle kinetic energy and therefore similarly, the amount of force required to bring a vehicle under control.  
 
For example braking distances are not just doubled with a doubling of the vehicle speed. They exponentially increase as shown in the attached chart of how long it takes to stop an average family car on a dry and a wet road.
 
 
This effect equally applies to cornering and manoeuvring forces when trying to negotiate a corner or avoid an obstacle.  The faster the vehicle speed the exponentially higher the ‘G’ force required to go around the corner and stay on the road.  In wet weather when the road surface is slippery it may not be capable of transmitting sufficient cornering force to go around the corner resulting in the vehicle sliding off the road!


Slow Down and Maintain a Safe Distance

As stated improvements in tyre and vehicle technologies over the years has progressively made cars safer to drive but nothing can overcome the laws of physics. If due to wet weather or for any other reason the road is slippery, increasingly at higher vehicle speeds the grip between tyre and road may not be sufficient to transmit enough force to stop the vehicle or negotiate a corner.
 
Hopefully this helps the understanding of the reason why the golden rule of safer driving, particularly in wet weather, is so important.  SLOW DOWN and allow more distance between you and the car in front.  If we all obey this rule it will help us all to avoid rear end accidents, loss of vehicle control and even save lives!
 

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