Control Systems & PLC's

Drive Speed

The Role of Anticipation While Driving

There is nothing exciting about the skill of planning ahead. Most driving skills taught at an advanced driving course might deal with dynamic aspects of cornering, with rally-driving oriented techniques of turning the wheel, with a driving position based on the position in a road-car racer, with emergency braking and even with skid control. However, planning ahead might weigh just as much as all of these skills combined. It allows to avoid the hazards and not get into emergency situations, and it is applied all of the time in every drive.

New driver usually drive based completly on reactions: Something happen, like a car in front stopping on their lane or moving into it, a pedestrian crossing the road or whatever mondane driving situations -- and they react. This kind of driving is very natural, but might in some cases bring you too close for comfort, breeding stress and increasing the risk.

In even more severe situations, where another driver makes an acute mistake like swerving into your lane from the lane of opposite traffic, the ability of the reacting driver to respond is not practical. However, as experience is gained, drivers learn to look further ahead and anticipate things in a greater advance. The problem is that this process does not always achieve efficient results and the driving style remains jerky and unplanned.

 

Telling the Future on the Road

Planning ahead, i.e. knowing what you are about to do before you actually do it, helps make driving easier, cheaper and safer. The basic rules that have to exist for planning to take place begin with concentration in driving. Many people consider driving to be a simple and natural skill and shut off their mind and go into a mental "Auto-Pilot" state of awareness. This couldn't be further away from the truth. If driving is so simple, how come that -- with all the rules, advanced roads, safe cars and law enforcement, millions die on the road in collisions, and many more get injured?

Driving is a complex task, but acquiring the skill of proper planning can simplify it and turn it to be very easy. In fact, the same drivers who don't mind their own driving, suffer from more stress and rage related to their driving. Once formed into a habit, planning makes driving more easy and natural. It also allows to reduce mechanical wear, gas milleage and air pollution by dozens of precents.

The second term that forms the base of good observation, is looking further ahead. The natural tendency of a human driver, based on years of moving at a walking pace, is to look straight ahead. The road is essentially raw information that our mind has to recieve and anaylse. However, we are moving relative to the road at pace much faster than walking and often faster than the analytical ability of the human mind. The natural way of dealing with all of this information is to ignore large amounts of it through what is called "Tunnel Vision." Drivers stare at a small stretch of taramc closely in front of them with a great focus. This reduces the overall amount of information, but a lot of important information is left out. Also, because this stretch of ground is lied just before the driver, the time left to analyse the information is reduced.

If you drive at a modest speed of 30mph (that is, 50km/h), you travel a distance of 13.9 meters per second. If you only look 15 meters ahead that all you have is little more than a second to react to whatever it is you see. This forces you to brake harder and veer much more sharply. If you could have responded earlier, you could have braked with much more ease, while also having time to notice the traffic behind, and you could steer much more gently, while also noticing traffic besides you.

The best way of noticing hazards earlier is to look further ahead and physically see them earlier. How far ahead to look? As far as you can see down the road in a direct eye contact. This should be about 15 to 30 seconds in advance, and in highways the distance can be as much as one kilometer in advance! This enables to anticipate hazards in the greatest possible advance, and react to them as progressively as possible. You see the hazard, plan what you are about to do, and than execute your plan.

 

But, what about the road between me and the horizon?

The typical question that rises at this point is in regard to closer elements. I have two answers to this: The first is two words -- Peripheral Vision. When I speak of looking far ahead, I refer to our foveal vision, which is the little field of focus that enables us to focus and notice details. This kind of vision, because of it's properties, should be used for observation and planning (based on the details it can notice). However, we have another, wider, field of vision and this is our peripheral vision.

Training the kind of vision helps in getting a very wide (albeit blurry) perspective while looking far ahead. Anything between you and the point of focus will be seen as blurry colors and sudden movements, which is more than enough. With training and experience you learn to rely heavily on the peripheral vision, much like race drivers, jet pilots and bikers. It can be very sharp. And it not like you can't take a short "peek" with your foveal vision.

Entering every road section, you need to move your eyes in a scanning motion from your immediate sorroundings to the horizon, and than use your imagination to visualize the line you want the car to take from where you are to where you want to get to (the furthest point on the road ahead) and keep you eyes "high." This brings me to the second point: If you look and plan 20 seconds in advance than the objects directly in front of you, say three seconds ahead, are what you saw 17 seconds past, so you don't need to look straight at it.

This kind of sight also yields additional advantages. The first is accuracy and smoothness. If you are looking one kilometer ahead, your steering corrections will be greatly reduced, because you become much more away of every little unwanted movement of the car. If you are looking ten meters ahead, and your car swerves slightly to the right you will not notice it, but if you are looking to the horizion, any little movement of the car will result in a very significant shift of your point of focus. By looking further ahead our mind can "calculate" the most straight path between us and our remote point of focus.

 

Reading the Road Surface

Our vision can help us anticipate or avoid slippery surfaces by noticing them when they are in our focus at the far end of the road. A big puddle of diesel, for instance, can be detected as a shiny, colorfull sheen, which can be than be driven around or driven over at a greatly reduced speed. This skill is also used in more mondane situations where we need to adjust our speed and position to the conditions. We can identify the surface we are driving over, asses the grip levels and choose whether and how much to reduce speed.

 

Adjusting Speed and Position to the Conditions

Our speed and our position (the lane in which we are driving and even our position inside the lane) have to be changed constantly while driving so it can match the conditions. There is a ground rule which is to "adjust speed so you are able to stop well within the distance you see to be clear, and that you know would remain clear." But it goes further than that. We need to asses the situation and every thing that can allow us to drive faster or that might force us to drive slower:

- The Road Surface: Quality-paved, rugged, dark tarmac offers better grip and allows to drive faster than worn, poorly-paved grey-looking tarmac.

- The Road Conditions: A wet road forces a slow down, and an even greater one where presence of grease of a deeper water film is anticipated. The same applies for conditions like sand on the road, snow, ice, etc...

- The Construction of the Road: How many lanes in each direction? Is there a divider? A Dual Carriageway with two lanes in each directions and a divider in the middle allows to drive much faster than on a two-lane roadway without a divider. It's also recommended not to drive as fast on roads without a quality divider -- a rigid "New Jersey" Concrete guardrail or a "W" steel rail are not as safe as newer types.

- Direction of the road: Driving on bendy roads is naturally slower than straight roads. Look ahead and asses the steepness of oncoming corners and whether they are followed by a straight or a successive corner to assume how much you need to slow down. The direction of the road also relates to inclines like driving downhill (again, depending on how steeply) and a "camber" angle.

- Width of the Road: Other than how many lanes, how wide are the lanes? Is there a shoulder? Is it a hard shoulder or a gravel shoulder? How wide is it? What is the height difference between it and the road? The hardshoulder is a potential escape route which facilitates faster driving speeds relative to roads with a gravel shoulder.

- Visibility: Full, bright daylight, late afternoom, night, fog, shade. Even a slight tree shade hinders visibility and increases risk relative to full day light.

- Driver allertness: How well rested is the driver? How focused are you on driving? A more alert and focused driver can drive at a faster speed, where the same driver can sometimes be less attentive and will have to slow down. We all have "bad days" where we need to slow down, and likewise we need to slow down to a speed which matches our feeling of safety.

- Typical Hazards: Children can be expected around schools, animals can be anticipated in the woods and country-side.

- Traffic: How dense is the traffic around you? What are the characteristics of the drivers around you? If the traffic around you includes a lot of trucks, you should slow down more. Also, you can anticipate that, on spring time, many cars be loaded with baggage and full of passengers, and their drivers might not be as attentive, so you need to slow down a bit more. On two-lane roadways, you also need to notice the oncoming traffic, it's density, proximity and speed and note any driver who illustrates signs of agression or lack of vigilance.

- State of the Car: Older cars, heavy trucks and poorly maintained vehicles needs to be driven slower than newer, well-maintained cars. Systems like ABS and stability control also improve safety, and the state of the tires and dampers is especially important. If any of the two is about to be replaced, now is not the right time to be pushing the speed limits. Also, you are not going to drive a new car as fast as you do a car that you are used to. The load on the car should also be brought into account.

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Why do people drive the speed limit in the far left hand lane?

I know the speed limit is the same in all lanes, but the far left lane is designated as a "passing lane" and used to pass slower vehicles. If you are not passing and are driving the speed limit (or under the speed limit), why would you drive in the far left hand lane? I can never figure this one out.
I was alive when it was 55. I drove then too. If you are that old, then you should be old enough to have been taught driving ettiquette. Drive in the right, pass on the left... What is the deal with the "magical left lane" anyway?

We in australia have the same problem, it is very annoying, the police here can book you for holding up traffic in the wrong lane, but it still happens a lot.

I Can't Drive 85! (Texas's New Speed Limit)