The IAM's Advice
Bryan Lunn is Chief Examiner for the Institute of Advanced Motorists (IAM). This article written by Bryan and published in Advanced Driving Magazine in Spring 2004 contends that driving in 3rd gear in a 30 mph can help to avoid exceeding the limit without being uneconomical.
"Speed for the hazard - gear for the speed"
Roger Harrabin is Transport Correspondent on the BBC Radio 4's 'Today' programme. He's also a friend of the IAM; he contacts us occasionally about motoring stories and he gave an interesting presentation on the media's perception of road safety at the IAM National Conference last October. Roger has had an open invitation to come to IAM Head Office to experience advanced driving for himself. Despite being a very busy journalist, he recently took us up on the offer and spent a day with Trevor Poxon, the Assistant Chief Examiner, who introduced Roger to advanced driving and some of the skills and techniques.
Trevor quickly noticed that Roger routinely had difficulty in keeping within the 30mph speed limits because he was going up through the gears too quickly, to reach top gear as soon as possible. Roger didn't realise that he was unconsciously increasing the power to ensure the ride was comfortable in the higher gears and that this was causing him to drive too fast in the 30 mph speed limits. Trevor explained that in typical built-up area driving situations, moving up through the gear box to fourth or even fifth gear automatically and as quickly as possible may lead to an unnoticed increase in speed just when you need to keep it at or under the 30 mph speed limit for road safety purposes, and to avoid setting off a speed camera. It was all a bit of a revelation to Roger and he's not alone in this; many drivers just don't realise that an increase in speed is a consequence of unnecessarily changing up to the higher gears. They also don't realise that third gear is a very flexible gear in modern cars and that it's the ideal gear when you need to keep your speed to 30 mph, or under.
Police drivers and IAM advanced drivers are taught to get their speed right for a particular hazard, or for particular circumstances, and then select the most appropriate and flexible gear for that speed; it's the old Police Driving Instructors' maxim, "speed for the hazard - gear for the speed" and it's a recognised advanced driving technique.
Roger later asked us if we thought the 'inappropriate gear' fault might be one of the reasons why so many motorists are 'flashed' by speed cameras when they are just marginally over the 30 mph speed limit. We told him that it is a contributory factor; many drivers in manual cars could avoid being 'flashed' by a speed camera if they used the interim gears - especially third gear - more often and for longer in urban driving situations.
In December, following further discussions with Roger, the IAM and the 'Today' programme commissioned MORI to do some research to establish whether driving in an inappropriate gear actually was causing some drivers to exceed the 30 mph speed limit. Motorists who exceed the speed limit by a considerable margin were not the focus of the survey; the research was confined to drivers likely to commit 'marginal' speed violations in 30 mph limits.
The poll drew on a survey base of 1000 participants, all of whom had manual transmissions; 79% of them said they had modern, five speed gear boxes. MORI took a typical 30 mph urban driving situation and asked: "Do you ever find the car tends to 'creep' above 30 mph without you realising it ?" 74% of those taking part in the poll answered "Yes". They were then asked what gear they would normally be in to maintain a steady 30 mph. Nobody was allowed to just say "top gear"; the pollsters were told to establish which gear drivers actually used when they were trying to do a steady 30 mph. 54% of the drivers polled thought that they should be in either fourth or fifth gear.
The IAM/Today programme sponsored research is probably the first that has focused on why drivers commit speeding offences by analysing this particular aspect of driver behaviour. It suggests that selecting the most appropriate and most flexible gear for the speed is a simple, practical step that individual drivers can take to curb their speed and avoid prosecution. But, selecting the appropriate and most flexible gear for the speed isn't enough on its own. You also have to use good acceleration sense too.
Acceleration sense is the ability to vary the speed of the vehicle in response to changing road and traffic conditions by accurate use of the accelerator. Acceleration sense requires informed driving experience, careful observation, full anticipation, sound judgement of speed and distance and an awareness of the vehicle's capabilities. By using third gear and accurate acceleration sense you can stay within a 30 mph speed limit quite comfortably in most modern manual cars, without putting any strain on the engine, the gearbox or the transmission.
Developing your acceleration sense will also help you to avoid unnecessary braking in urban and sub-urban driving environments too. Braking, even at around 30 mph (44 feet/14 meters per second), is a destabilizing influence on the vehicle. But if you can vary the speed of the vehicle in response to changing road and traffic conditions in 30 mph speed limits just using the accelerator (acceleration sense), you have a finer level of control of your vehicle and your speed.
We know that getting the speed right for a particular hazard or for particular circumstances and then selecting the most appropriate and flexible gear for that speed ("speed for the hazard - gear for the speed") is pretty much common sense as well as being a sound driving technique. Surprisingly, we've had a few critical comments following Roger Harrabin's piece on the 'Today' programme and other interviews we did subsequently. Those drivers who criticised the IAM's advice about using third gear to avoid exceeding the 30 mph speed limits suggested that it's less economical and less environmentally friendly.
They are actually the drivers who are potentially compromising road safety and end up paying unnecessary speeding fines. They are also the drivers who are using more fuel than they really need to and are polluting the environment.
The IAM's Advice on the Use of Gears and Advanced Driving
Advanced Driving is all about being in the right place at the right time, travelling at the right speed with the correct gear engaged. In other words, "Speed for the hazard - gear for the speed".
Using the gears correctly is a basic requirement of advanced driving; select the right gear before reaching a hazard and use the intermediate ratios whenever necessary, including for brisk acceleration.
Properly co-ordinated gear changes are smooth and precise without any jerking, and passengers do not usually notice them. A smooth downward change requires a little pressure on the accelerator pedal to match engine speed to the road speed when the drive is taken up again.
Do not change down through the gears when slowing down. It's "brakes to slow - gears to go", except in an emergency. You can use the lower gears for maximum engine braking going down a steep hill or on a slippery road where you might skid, or if your brakes fail.
Don't ride or slip the clutch, or coast to a stop with the clutch disengaged.
Automatic gearboxes remove most of the need for decision-making about gear changes in normal driving conditions. But, always consider the advantages of using the intermediate 'hold' positions when brisk acceleration is needed.
Recent research by the IAM and BBC Radio 4's 'Today' programme looked at why some drivers exceed the 30 mph speed limit. The research was confined to drivers likely to commit 'marginal' speed violations in 30 mph limits, not those that greatly exceed the limit. All the participants had manual transmissions and 79% had modern, five speed gear boxes. Drivers were asked: "Do you ever find the car tends to 'creep' above 30 mph without you realising it?" 74% of those taking part in the poll answered "Yes".
They were then asked what gear they would normally use when trying to maintain a steady 30 mph. 54% thought that they should be in either fourth or fifth gear.
The research is thought to be the first looking at driver behaviour and gear selection. It suggests that selecting the most appropriate and most flexible gear for the speed is a simple, practical step that individual drivers can take to curb their speed and avoid prosecution.
But selecting the appropriate and most flexible gear for the speed isn't enough on its own. You also have to use good acceleration sense.
Acceleration sense is the ability to vary the speed of the vehicle in response to changing road and traffic conditions by accurate use of the accelerator, and it requires careful observation, full anticipation, sound judgement of speed and distance and an awareness of the vehicle's capabilities. By using third gear and accurate acceleration sense, you can stay within a 30 mph speed limit quite comfortably in most modern manual cars without putting any strain on the engine, the gearbox or the transmission.
Developing your acceleration sense will also help you to avoid unnecessary braking. Braking, even at 30 mph (44 feet/14 meters per second) can destabilize the vehicle. But, if you vary your speed in 30 mph speed limits by just using the accelerator (acceleration sense), you have a finer level of control of your vehicle and your speed. You can also improve fuel consumption and minimise expensive wear and tear on your car too.
Optimum economy levels aren't just about the engine and road speeds; throttle openings are important factors too. You actually consume a lot more fuel, and you are much less environmentally friendly, if you are in a high gear (fourth or fifth) at a low road speed (30 mph or less). That's because the throttle opening has to be wider to address the imbalance between the inappropriate gear and your speed. More fuel is admitted into the manifold and the engine, and the result is that you tend to increase your road speed. But, if you select a more responsive gear (third) for the same road speed (30 mph or less) and you use a "light right foot", the throttle opening will be narrower and less fuel consumed. Smoother driving gives you better control of the vehicle and improved passenger comfort - plus it's more economic and more environmentally friendly.
For information on any other aspect of driving or riding please visit the IAM iam.org.uk.