Weather and Driving

Master Driver Joined: Mar 27, 2010 Posts: 209

Weather has always had a crucial effect on human life (and life in general). In the modern (or post-modern) world, perhaps one of it's most dramatic impacts is it's effect on traffic. Shifts in the weather will cause changes to traffic movement, collisions and other related subjects. This article will deal with driving and safety measures related to these subjects.

Meteorology
If the earth circulated the sun in a perfect square shape, we would not have winter and summer. Similarly, if the earth's surface was fully flat, we would not have different climates. In practice, the earth's shape makes the air flow move about in a twisty route that makes it ascend and descend. The great precentage of water on the earth's surface intesifies this process, as flows like the gulf flow absorb and transport heat from one place to another.

Popular Synoptic maps (which should suffice for all of us) rely on measuring air pressure at two levels: The surface level and the given height at which the pressure is 500 millibars. I repeat: The measurement takes place at the height in which the pressure is 500mb. The result is that the synoptic map you see on the forecast portrays lines of height that all share the pressure of 500mb.

So the map actually describes a certain three-dimensional map, a surface in mid air, which has highs and lows, like hills and valleys or -- low-pressure areas and high-pressure areas. A low pressure area is a "valley" that forces the air and clouds around it to fall into it, creating cloudy weather and increased chance of parcipitation. A high-pressure area works like a sloped hill, making clouds fall off, clearing the weather. The movement of clouds in and out of such areas is in a circular shape (like when you open a pluged sink) like a typhoon.

A low pressure area will generally be created when at least one of the three conditions hold true:

- A boarder between a typically hot area and a cold one. Cyprus, for instance, forms a boarder between a colder sea and a hotter land.

- Over a particularly hot area

- Over a steep downhill slope coming down from the high mountains (as they block free air flow).

Also, the air movement (wind) from a high pressure area to a low one can create a situation (when not too close to either of the earth's poles) where different air flows collide and create a "weather front." The weather front can be neutral, without any unique effect. However, a cool wind can run under hotter air and push it up to create a "cold front." With sufficient moist, a Comulonimbus cloud be formed and rain and winds will be likely (although not definite). Such a cloud can be identified as a big white-grey cloud with a relatively low bottom, which reaches very high up. Google it to get a better idea of how it looks.

The other option is for the cold stationary air to withdraw as the hotter air goes over it and covers it, creating a hot front. This front is identified by thinner, wisplike clouds that seem to stretch further into the horizon. These can creat light but consistent drizzles. For rain in particular, you can also check your local rainfall radar for practical information as to the amount of downpour and it's track over your country for the near week or so. Now we go for the actual driving.

Winter Driving
Winter causes two problems. The first is reduced grip levels and the second is reduced visibility. We can roughly state that the colder it is, the more slippery it is, and the more collisions be caused due to impaired road grip and not so much as reduced visibility. There is nothing to fear about winter driving. It can be done without a lot of problems and not few are those who enjoy it.

Proper winter driving (like proper driving in all conditions) begins with doing whatever you can do before you drive, to improve your odds while driving. The first point is your tires. This is just a good place to stress the main points I talked about regarding tires in another article. The first point to realise is that most of the modern, steel-belted tires don't become defected because of a shallow tread depth (which most authorities put a stress on) but rather by less detectable wear caused by "heat cycles" that the tire experiences during the day and night, weather changes and driving.

A tire should be replaced at roughly about 3 years of age or 70,000km -- which ever of the two comes earlier. In countries with a weather than is more constant and cold tires can last a bit more, about 4 years or 80,000km. If the car is regularly parked in the shade and not driven as much, the life spawn can increase slightly in either case.

And, if you do experience significant wear of the tread, than do not settle for the legal limt of 1.6mm (elapsed as 2mm). A new tire comes with about 9mm of tread depth that can channel about 10 liters of water per second (!). If you drive at 60mph over a thin film of two millimeters of water, than your tires have to clear out four liters. If we reduce tread depth to even two milimeters, the maximal ability to channel water is two liters and the tire will hydroplane with zero grip. Even at a conservative 30mph it will be like driving on snow. If a tire has 3mm or less -- it should be replaced.

Tire presure needs be checked too, at least once every two weeks. During travel, the tire builds up temperature and the air inside heats up. If you feel warmth on the tire's sidewall or under any doubt -- inflate by additional 10%. In any case, this kind of over-inflation will not reduce grip levels, it would increase them. The tire will recieve a concave shape that will allow it to run through the water and onto the tarmac. While it is advised to stick to recommendations, inflating tires regularly with an additional 2 to 3 PSIG is perfectly reasonable. The air pressure should be changed if the tires are hot or if the car is loaded with passengers/luugage.

In extremlly cold weather, the tire will experience an opposite effect where the air will condense and the tire reading will show a decreased pressure. The tire is cold and the air inside it is condensed but the actual shape of the tire remains identical. When you need to inflate tires, inflate them to the cold pressure. For every extra ten farenheit less, the pressure will be reduced by one PSIG.

Understand: you don't need to deflate the tire. For example, you filled the tire with recommended 30PSIG. Now it's winter and temperatures descend by 30 degrees, the air inside the tire will condense and when you check it, it will read 27PSIG. You don't need to physically deflate it by another 3PSIG. But you do need to reinflate it with 27PSIG instead of 30, so long as the cold temperature reign. Again, if in doubt, always over-inflate.

Winter driving itself should be done slowely. About 20% less than on the dry. The following distance from the car ahead needs be increased from the default 2 seconds on the dry, to four seconds on the wet, and ten seconds in snow/ice. The driving inputs should be smooth and accurate, but not slow. I see people turning the wheel all too slowly or people who are afraid to press the brakes -- all needlessly.

Another step is to asses road grip, as this varies more widely on the wet. A typical thin film of 2mm of water reduces grip levels from 0.7 to 0.6 and less with deeper water (0.5). Another problem is that the road is constantly littered with dust, dirt from cars, oil drips froms engine gaskets, oil filter/valve/pan, U-rings, etc. This dripping of lubricants is more dense in areas of slow moving or standing cars, and especially in traffic of heavy vehicles (which move moving parts that need be lubricated). The result is greasy surfaces around intersections, bus stops, winding roads, areas prone to heavy traffic. This build up soaks into the tarmac and carries a relatvielly little effect on the dry.

When wet, however, the dirt and oil float and reduce grip levels twice relative to a "washed" wet road. This is true for the first day or two of rain in the winter, after the summer, but it can also be experienced after a certain period of clear sky, depending on the amount of dirt and oil buildup. Again, slower areas like winding roads or city streets can "grease up" within as little as five days, but open highways can somes stay clean for up to three weeks. It's best to relate to every rain following a dry week as one that sets grease aflot.

Still, it's important to identify more slippery pavement segments, either because of their location (bus stops, intersections, etc...), visual presence of grease, dirt, mud, fallen leaves and alike; road alongside tree lines, fields or in-town construction sites; far edges of the road and the bottoms of sloped road sections. It can so happen, on a long trip, that part of the road be simply wet, while another part will be horribly greasy, because that area of the road experienced a longer dry period. Tarmac quality also has an impact -- bright-looking tarmac is always slippery, but especially in the wet.

Snow, sleet and Ice will about three times as slippery as that! However, they include a whole range of distinctive surfaces: Frost is a result is moist condestion in the early morning, which becomes frozen by a sudden breeze from the mountains. This frost is slippery, but not nearly as much as actual snow. Similar grip levels are experienced by hail (which is created by unqique turbulances in rain clouds). Even different snowy surfaces can create different grip levels. Thin, fresh snow is still quite grippy. Cold, thick and possibly densed snow is highly slippery, much like ice.

Essentially, that is what ice is all about. It is snow that became so highly pressurized as to become rigid. Ice is extremlly slippery and needs to be avoided. The problem is that sometimes a small patch of ice can be left semi-metled under tree shades or inside a puddle of water. The layer of ice is thin and unnoticable, and is thus called "black ice." However, if you are looking for the lowest possible grip levels, you can find those in ice when it's at 32 farenheit. At this temperature you get just ice, with a thin film of water over it and with no snow what so ever -- which is absurdly slippery.

Ice requires special ice tires with studs. Snow requires snow tires (and not M/S tires or winter tires) and deep snow requires chains. Don't settle for M/S tires for anything which is not very thin snow, and don't use snow tires on the dry either.

Also avoid deep puddles. The deep layer of water can cause hydroplaning which is just as bad as driving over ice. The puddles can also spray water on other cars/pedestrians, or on the car's electric components or into the air filter, causing a hydroblock which shuts down the engine and maybe ending it's life. It can also hide ice or a rock. Either go around them or slow down as well as possible before them. Driving over puddles needs be done in a straight line and with a light tread of the gas pedal. Even if a momentary hydroplaning occurs, don't jerk off of the gas and don't dry to make steering corrections, even if the water tries to "push" the car sideways. Chances are that the inertia will keep you in the right direction. Steering corrections will spin you around.

You need to be ready for the option of emergency braking during the winter. Even though it's wet, or even snowy/icy -- don't be afraid to brake hard. With ABS, loud sounds and vibrations will be noticed, more noticable as the surface is more slippery. This is the sounds of the normal function of the ABS system. This allows you to stop in a reasonable stopping distance and be able to steer around an obstacle, while braking, should the braking distance not suffice. Don't hesitate while braking, don't let go of the pedal and don't choose to steer instead of braking. First kick the brake pedal, than choose what to do further.

Without ABS you should use an advanced/defensive driving trainer/course to acquire the skill of regressive braking. This is a technique where you first tread the pedal, which locks-up all wheels, and than you starts to gently ease off of the pressure untill you find the point of threshold where the wheels are no longer locked, and than you keep the car on that threshold by constantly easing back on the brake pressure as the speed is reduced.

For the unskilled it might be better to brake hard and lock the wheels, and let go of the pedal when you need to steer. On ice, this technique can be replaced for cadence braking where you pump the pedal. The combination of actual ice and a low skill at regressive braking is the only condition where cadence braking is legitimate.

Very rough weather of heavy downpour of rain, snow storms and high winds might be a good idea for choosing not to drive in the first place. In heavy-winter, when you do drive, try to arrange your schedule so that you have plenty of time to reach your destination.

Anticipate sudden winds, splashes of water or sudden downpours. Some roads are enclosed by walls or cliffs on both sides. As you exit the "sheltered" part of the road in a stormy weather, you will experience a sudden blow of wind. Get ready and grip the wheel firmly and place yourself in the middle of the lane. Splashes of water can be anticipated when a car in the opposite lane crosses a deep puddle of water. Apply your wipers in advance.

Rain can be identified in the formation of the clouds I stated earlier and by the acustics of lightning. When you hear the lightning and thunder directly one after the other, it means that you are in the middle of the storm. The greater the gap, means the greater the distance from the eye of the storm.

When you look up at the road ahead, look at the sky as well. Look for an area where the base of the cloud looks exceptionally low and dark, and -- if possible -- look at how high the cloud's upper extention (which should be anvil-shaped) towers. An area of the cloud with a low, dark base and a tall anvil is the base of the cloud and can surprise you with a sudden intense downpour.

Summer Driving
If you thought winter driving is dangerous, wait untill you hear about the summer. In countries that don't experience very hard weather, the summer creates a higher precentage of collisions with injured and dead passengers. There are more drivers, some less experienced, longer milleages and heavier traffic and more pedestrians.

Returning to car maintainence, most people remember that their tires require maintainence only during the winter, because it's slippery. In fact, they are just as crucial in the summer. In the summer, we can still experience slippery conditions, like small locative downpours (which become hopelessly greasy), as well as constant pressure of grease and dust. Sand on the road is more slippery than a wet road, and mud on the road can be just as slippery as snow. Sometimes, heavy vehicles even drop an actual "pool" of oil which becomes a death trap like snow or ice.

Tires also fail in the summer due to increased wear and a chance of blow-out under the heat. Ensure proper inflation. Remember than if you got to the station with hot tires, you need to inflate it with an extra 10% or even 20%. The over-inflation will not reduce grip and will NOT increase the risk of a blowout -- on the contrary, at most it will increase grip and reduce the risk of a blowout. Cars also require different pressures when they are loaded with passengers or baggage. Even three adult passengers in the back can make a car "loaded." You also need to maintain your dampers. These should be replaced between 70 to 90,000km, depending on how much cargo they usually carry and how smooth are the roads they usually cope with.

All passengers must be harnessed with the seatbelts. I don't just mean put it on, the seatbelt must fit carefully over the pelvic and the middle of the shoulder. Children should be placed the appropriate child restraint or booster, and pets also have special harnesses for them. Head restraints are also a formiddable safety feature. Adjust them in line with your eye brows and as close to your head as possible.

The driver must focus on driving. His/her mind should be on the road ahead and he should not turn around or even use the interior mirror to check on the inside of the car in family trips. Families should have a partner (the wife/husband or the older child) which should ensure quiet, proper conditioning and order within the car. It's also important to take breaks. The breakes do wonders with the driver's concentration, with the frustration amongst the children and with the tires, dampers and engine.

In a drive shorter than two hours, you can drive straight through. In a two-hour long drive, it's advised to take one break of ten minutes after 50 minutes of driving. In a drive of three hours, take two breaks at about the same intevals, and in longer trips make breaks on an hourly basis.

Try to avoid to risk of being stuck the open hard-shoulder of the highway. Most people stop therein for the most unjusitifed reasons: a need to pee, a phone call to answer, looking at a map, taking the kids outs, resting and what not -- stopping for any of these reasons can be delayed to a safe stopping place which is partitioned from the road. Likewise, stopping due to fatigue, neglegible mechanical issues, or to help another stuck driver -- should all be avoided.

In fact, even if you experience an acute mechanical issue, like a blown tire or an increase of engine heat, it is possible to keep on driving, preasuming there is a safe stopping place available within a reasonable range. Yes, even if your tires blows out, no matter if it's the one facing the road or not, it is possible to flush right, slow down to about 10km/h and crawl to a safe stopping place and replace the tire.

If you must stop for some reason, get everyone out of the car and away from the road (over the guardrail or trench and away from it). Don't try to fix anything, just get to safety and call emergency services. If there is no safe place to go to, stay buckled inside the car and keep the brakes clamped on.

Glare is another issue with summer driving. I'm not talking about dazzle from the other drivers' high beams at night (which will be dealt with in a different article) I am talking about glare that comes from the sun in one of three forms: The first form occurs on open roads at the peek of the heat, where the tarmac (which can reach a temperature of 70 degrees celsius) generates vapour which reflects sun rays, creating a certain blur or glare (a "Fata Morgana"). This can be solved only by use of quality sun glasses, especially those with the little lateral extentions.

The other two kinds of glare are caused directly by the sun. The first is when we drive east in the early morning hours or west in the late evening, and we experience frontal glare as our eyes contact the sun in a shallow angle. The solution here is not shades but rather using the car's visor. The same glare can also be experienced laterally when driving north or south in the same hours, solved by tilting the visor sideways.

In countries with clear, sunny weather, it's best to use the switch on the bottom of the interior mirror and tilt it into "night mode." This is problematic in foggy or heavily-clouded weather, but in bright days it gives a "clean" image.

Another thing has to do with the heat built up inside the cabin when it stays under the sun. The solution here is to try to park the car in the shade, and cover the windshields and/or windows as possible. Some cars have plastic or bakelite steering wheels that are best also covered by some towel. If possible, even try to keep a slight open crack in one window.

Before entering a hot car, try to disperse the heat. The heat can be dihydrating and tiring, causing fatigue. There also likely to be particles from the plastic surfaces floating about. It's best to open the doors and wait for about two minutes. If it's really hot you might choose to turn the car on and apply the air conditioning on maximum air flow with "fresh air" setting, with the doors still opened, all while waiting besides the car.