Acceleration Nonsense
Discussion
My police driving career spanned two different versions of Roadcraft. My standard course took place in 1992 when the police were still teaching the seven phase system from the old blue Roadcraft, whereas I undertook my advanced training in 1995 in accordance with the (then) new five phase system.
For both courses, some commentary was required during the final test drives. On a standard course that was one drive with an instructor during which about 2 minutes of commentary was expected and on an advanced course you would have two final test drives (one auto, one manual) during which 10 minutes of commentary was required during each drive.
Commentary is not easy, especially for beginners, but one of the tips my instructors gave was to have some stuff in reserve for when there wasn't much to talk about. So when there was lots going on, you'd talk about the hazards, grading them in importance, what your plans were etc. but when you were on a featureless road with nothing much presenting as hazards, the tip was to throw in a few Roadcraft definitions.
You would describe the four advantages of the following position, talk about scanning, and throw in some verbatim paragraphs from Roadcraft and the Highway Code (even learning a few paragraph numbers for extra anorak appeal).
Having done two courses under two books, my repertoire was a bit of a mixed bag. To this day I can still remember two full definitions without (I promise) any reference to the books. Firstly braking sense from the old blue book...
"The ability of a driver to appreciate a situation and apply the brakes in a gradual and timely manner to stop, or reduce the speed of the vehicle where this cannot be achieved by deceleration alone."
And the old definition of acceleration sense...
The ability of a driver to vary the speed of the vehicle, by accurate use of the accelerator, to meet changing road and traffic conditions."
When the new book came out, these definitions were altered slightly and weren't as clearly identifiable from the rest of the text as actual "definitions", but they were still relevant and I included them in my advanced test commentary (and in my instructor's tests a few years later) without any negative comments or marks.
In my view, acceleration sense is one of the abilities which really separates a skilled road driver from the rest of the motoring public. It's a skill that very few people will ever notice, it's a skill which can be extremely difficult to learn, a skill which can be very satisfying to practice, a subtle and unobtrusive skill which can be used to fine effect on any and every journey and a skill which I doubt anyone ever truly masters.
It's also a skill which is based on the most simple of principles...
The accelerator works both ways.
I know this seems a ridiculously simple principle, but honestly, correct use of the accelerator is an absolute key skill in advanced road driving, no matter what type of vehicle you're driving. To be clear though, I'm not just talking about increasing the speed of the vehicle by pressing the gas pedal. Acceleration sense is much mure subtle and wide-reaching than that.
What I'm talking about is how you use the accelerator pedal whilst you're driving along, approaching and negotiating hazards, how you use the accelerator in reaction to changing road and traffic conditions, changing speed limits and changing gradients and how you use the accelerator to maintain a following position on other vehicles.
When I was teaching advanced police courses, I'd get my students to perform a number of exercises to improve their acceleration sense.
One exercise involved driving a road which included a series of different bends. Most drivers would accelerate between corners and then brake for the next corner (rinse and repeat etc.). Now, there's nothing inherently wrong with this approach, but I would ask my students to drive the road at a reasonably quick pace in a single gear (usually 4th) without braking. I would expect the corners to be negotiated correctly with a little acceleration for balance, and I'd expect some reasonable acceleration between corners, but the student's job was to assess the bends and pick the correct point at which they should lift off the accelerator to achieve the correct speed for the bend.
Another good exercise was to drive a section of NSL road leading to a reduced limit of 30 or 40 and get the student to practice bringing the car down to the correct speed before entering the reduced limit just by lifting off the accelerator.
I've heard a few people talk about how a good driver should never brake whilst driving on a motorway. This isn't quite correct, but the point they're trying to make is that if you extend your observations to the far distance, plan well and spot situations before they arise, then you should be able to deal with most speed changes on the motorway without having to touch the brakes.
There are a few things to bear in mind. Vehicles can vary dramatically in their response to a lift of the throttle. Diesels have a high compression ratio and tend to provide a little more retardation than petrol engines. Retardation is always more pronounced in lower gears than in higher gears. The vehicle's weight makes a difference - lighter cars will slow at a faster rate than heavier ones. It's particularly difficult to reduce the speed of a car with an automatic gearbox by lifting the throttle as they are much less responsive in this respect than manual cars.
You may have noticed that I've rambled on this long without mentioning "engine braking". This is deliberate.
If you need to brake, your car is fitted with a perfectly adequate braking system which has been kindly fitted by the manufacturer at no extra cost for this very purpose.
I'm actually writing about a much more subtle and unobtrusive use of the accelerator to vary the speed of the vehicle, rather than a quick change down and lift to dramatically reduce the vehicles speed. Using the gears to slow the car is a fairly basic approach and has some downsides. No brake lights are displayed by the slowing vehicle, for instance, and it can unsettle a car and lock wheels if done badly, which can be bad news in a RWD car.
Another very nice use of acceleration sense is during overtaking. When overtaking a car and slotting in to a gap behind the next car, it's very common for a driver to over-accelerate and then come in to the gap under brakes. Again, nothing inherently wrong with this, but here's a nicer method...
Once you've moved out and accelerated until you're alongside the subject vehicle, lift off the accelerator. You'll already have enough momentum to complete the overtake, but you should be able to slot nicely in behind the next vehicle without braking. It results in a less aggressive-looking overtake and is usually appreciated by passengers.
It can be very unnatural at first - lifting off when you think you should keep the throttle pinned, but once you've tried it a couple of times (in appropriately safe circumstances of course), you'll realise the benefits.
There are other benefits to improving your acceleration sense too. A 2 second following position is achievable through acceleration sense only, but any closer and you'll be dabbing the brakes regularly. It will also improve your extended observations as you'll need to spot evolving hazards earlier if you're going to negotiate them on acceleration sense alone.
You'll also be able to impress the ladies with your skills by pointing out the driver in front who has braked twenty seven times in the last mile whilst you haven't braked at all due to your superior skill. Trust me - she'll love it. Mrs Local almost woke up last time I showed her that one.
Anyway, I've rambled on long enough now. Go and play with your throttles!
For both courses, some commentary was required during the final test drives. On a standard course that was one drive with an instructor during which about 2 minutes of commentary was expected and on an advanced course you would have two final test drives (one auto, one manual) during which 10 minutes of commentary was required during each drive.
Commentary is not easy, especially for beginners, but one of the tips my instructors gave was to have some stuff in reserve for when there wasn't much to talk about. So when there was lots going on, you'd talk about the hazards, grading them in importance, what your plans were etc. but when you were on a featureless road with nothing much presenting as hazards, the tip was to throw in a few Roadcraft definitions.
You would describe the four advantages of the following position, talk about scanning, and throw in some verbatim paragraphs from Roadcraft and the Highway Code (even learning a few paragraph numbers for extra anorak appeal).
Having done two courses under two books, my repertoire was a bit of a mixed bag. To this day I can still remember two full definitions without (I promise) any reference to the books. Firstly braking sense from the old blue book...
"The ability of a driver to appreciate a situation and apply the brakes in a gradual and timely manner to stop, or reduce the speed of the vehicle where this cannot be achieved by deceleration alone."
And the old definition of acceleration sense...
The ability of a driver to vary the speed of the vehicle, by accurate use of the accelerator, to meet changing road and traffic conditions."
When the new book came out, these definitions were altered slightly and weren't as clearly identifiable from the rest of the text as actual "definitions", but they were still relevant and I included them in my advanced test commentary (and in my instructor's tests a few years later) without any negative comments or marks.
In my view, acceleration sense is one of the abilities which really separates a skilled road driver from the rest of the motoring public. It's a skill that very few people will ever notice, it's a skill which can be extremely difficult to learn, a skill which can be very satisfying to practice, a subtle and unobtrusive skill which can be used to fine effect on any and every journey and a skill which I doubt anyone ever truly masters.
It's also a skill which is based on the most simple of principles...
The accelerator works both ways.
I know this seems a ridiculously simple principle, but honestly, correct use of the accelerator is an absolute key skill in advanced road driving, no matter what type of vehicle you're driving. To be clear though, I'm not just talking about increasing the speed of the vehicle by pressing the gas pedal. Acceleration sense is much mure subtle and wide-reaching than that.
What I'm talking about is how you use the accelerator pedal whilst you're driving along, approaching and negotiating hazards, how you use the accelerator in reaction to changing road and traffic conditions, changing speed limits and changing gradients and how you use the accelerator to maintain a following position on other vehicles.
When I was teaching advanced police courses, I'd get my students to perform a number of exercises to improve their acceleration sense.
One exercise involved driving a road which included a series of different bends. Most drivers would accelerate between corners and then brake for the next corner (rinse and repeat etc.). Now, there's nothing inherently wrong with this approach, but I would ask my students to drive the road at a reasonably quick pace in a single gear (usually 4th) without braking. I would expect the corners to be negotiated correctly with a little acceleration for balance, and I'd expect some reasonable acceleration between corners, but the student's job was to assess the bends and pick the correct point at which they should lift off the accelerator to achieve the correct speed for the bend.
Another good exercise was to drive a section of NSL road leading to a reduced limit of 30 or 40 and get the student to practice bringing the car down to the correct speed before entering the reduced limit just by lifting off the accelerator.
I've heard a few people talk about how a good driver should never brake whilst driving on a motorway. This isn't quite correct, but the point they're trying to make is that if you extend your observations to the far distance, plan well and spot situations before they arise, then you should be able to deal with most speed changes on the motorway without having to touch the brakes.
There are a few things to bear in mind. Vehicles can vary dramatically in their response to a lift of the throttle. Diesels have a high compression ratio and tend to provide a little more retardation than petrol engines. Retardation is always more pronounced in lower gears than in higher gears. The vehicle's weight makes a difference - lighter cars will slow at a faster rate than heavier ones. It's particularly difficult to reduce the speed of a car with an automatic gearbox by lifting the throttle as they are much less responsive in this respect than manual cars.
You may have noticed that I've rambled on this long without mentioning "engine braking". This is deliberate.
If you need to brake, your car is fitted with a perfectly adequate braking system which has been kindly fitted by the manufacturer at no extra cost for this very purpose.
I'm actually writing about a much more subtle and unobtrusive use of the accelerator to vary the speed of the vehicle, rather than a quick change down and lift to dramatically reduce the vehicles speed. Using the gears to slow the car is a fairly basic approach and has some downsides. No brake lights are displayed by the slowing vehicle, for instance, and it can unsettle a car and lock wheels if done badly, which can be bad news in a RWD car.
Another very nice use of acceleration sense is during overtaking. When overtaking a car and slotting in to a gap behind the next car, it's very common for a driver to over-accelerate and then come in to the gap under brakes. Again, nothing inherently wrong with this, but here's a nicer method...
Once you've moved out and accelerated until you're alongside the subject vehicle, lift off the accelerator. You'll already have enough momentum to complete the overtake, but you should be able to slot nicely in behind the next vehicle without braking. It results in a less aggressive-looking overtake and is usually appreciated by passengers.
It can be very unnatural at first - lifting off when you think you should keep the throttle pinned, but once you've tried it a couple of times (in appropriately safe circumstances of course), you'll realise the benefits.
There are other benefits to improving your acceleration sense too. A 2 second following position is achievable through acceleration sense only, but any closer and you'll be dabbing the brakes regularly. It will also improve your extended observations as you'll need to spot evolving hazards earlier if you're going to negotiate them on acceleration sense alone.
You'll also be able to impress the ladies with your skills by pointing out the driver in front who has braked twenty seven times in the last mile whilst you haven't braked at all due to your superior skill. Trust me - she'll love it. Mrs Local almost woke up last time I showed her that one.
Anyway, I've rambled on long enough now. Go and play with your throttles!
BertBert said:
I find this interesting. I understand and agree that the exercises are good. But that doesn't persuade me that the exercises are actually best practice. I quite like using the brake. I don't see anything "advanced" in a driving style that seeks to all but eliminate brake use. Why is it desirable? Clever yes, but what *real* benefit?
Bert
I suspect you've taken my post a little too literally.Bert
Acceleration sense is just one of a range of skills used by a good driver. The excercises I described are designed to help you practice acceleration sense so that you can then incorperate it into your other driving skills.
I don't advocate trying to drive everywhere without using the brakes. I would be very concerned if anyone thought I was advocating not using brakes, so I'd like to clear that point up.
Braking sense and the ability to apply the brakes correctly are another skill used by a good driver - I'd just seperated acceleration sense out to share my thoughts as I have done (and intend to carry on doing) with a broad range of seperate skills and abilities.
Use acceleration sense where appropriate (such as rolling in to a following position on a slower car rather than rushing up to it and then braking). But please - where it is appropriate to brake, you should brake.
I'll cover braking at some point soon, but some key points:
Early and lightly,
Three phase braking,
Tapering on and off,
More to follow!
Rick101 said:
I've done IAM and find their message quite confusing. I've had mixed messages and can't understand whether it's about safety, economy, or performance!
Personally, I'm not in the slightest bit bothered about fuel economy or saving pad material etc. I drive with mechanical sympathy, but I drive for fun, not tootle along on a fuel saving exercise!
I understand your confusion. Keep,coming back to the forum - I've a couple of pieces forming in my mind that I'll commit to posts over the next few weeks, one of which will be an examination of the true meaning of "advanced" driving.Personally, I'm not in the slightest bit bothered about fuel economy or saving pad material etc. I drive with mechanical sympathy, but I drive for fun, not tootle along on a fuel saving exercise!
Craig85 said:
In fact I would say that acceleration sense is far more important when driving in town, or certainly when amongst other traffic. This is because you have other to not only read the road to make smooth efficient progress, but the actions of other drivers, and even the effect of traffic lights etc on your drive.
This is a very good point and I probably should have gone in to more detail on the use of acceleration sense in an urban environment. I received a PM from a PH member the other day requesting a post on urban & city driving so I'll include some acceleration sense stuff in that when I write it.Craig85 said:
Finally, I am not an advanced driver so this is probably rubbish but I have always practiced trying to make sure I am at the correct position in the road, in the correct gear and at the correct speed at any given moment.
That depends on your opinion of what exactly an advanced driver is (see the other thread). If you're thinking along those lines and looking to improve then you're already taking on some of the principles which go to making you an advanced, or better, or more skilled driver - whatever you want to call it.What is your concern as you approach the HGV? Is it that the driver may be tired / inattentive / on the phone? If it is, then this is one of the situations where a horn warning would be wholly appropriate.
My concern would also be that the driver was lost & looking for a turning which opens up the possibility that they will either turn right or change lanes with little or no warning.
So, to answer your question, keeping your time alongside such a vehicle to a minimum with a burst of acceleration would be perfectly acceptable, but I'd be tempted to give a short horn warning whilst looking for visual clues about the drivers intentions. Look at them in their door mirror - are their eyes on a phone? Are they looking intently at every junction? Have they looked at you? There are always some observation links to pick up on if you look in the right places.
My concern would also be that the driver was lost & looking for a turning which opens up the possibility that they will either turn right or change lanes with little or no warning.
So, to answer your question, keeping your time alongside such a vehicle to a minimum with a burst of acceleration would be perfectly acceptable, but I'd be tempted to give a short horn warning whilst looking for visual clues about the drivers intentions. Look at them in their door mirror - are their eyes on a phone? Are they looking intently at every junction? Have they looked at you? There are always some observation links to pick up on if you look in the right places.
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