Roadcraft - Police Driver's Handbook PDF

3c i (Chapter 4 - Anticipating hazards in the driving environment 71 %i Use dipped headlights: in built-up areas with street lights in situations when dipped headlights are more effective than the main beam - for example, when going round a left-...

3c i (Chapter 4 - Anticipating hazards in the driving environment 71 %i Use dipped headlights: in built-up areas with street lights in situations when dipped headlights are more effective than the main beam - for example, when going round a left-hand bend or at a hump bridge ® in heavy rain, snow and fog, when these reflect glare from your headlights on full beam. Dip your headlights to avoid dazzling oncoming drivers, the driver in front or other road users. When you overtake another vehicle, return to full beam when you’re parallel with it, Only use fog lights when visibility is 100 metres (328 feet) or less. Always drive so that you can stop safely within the distance you can see to be clear on your own side of the road. At night, this is the area lit by your headlights unless there’s full street lighting. Even in the best conditions your ability to assess the speed and position of oncoming vehicles is reduced at night, so allow an extra safety margin. If you use a satnav at night, make sure it's positioned so that it doesn’t obstruct your vision in the dark, and its screen doesn't dazzle you. Use the aural prompts whenever possible. Following other vehicles at night When you follow another vehicle, dip your headlights and leave a large enough gap so that your lights don’t dazzle the driver in front When you overtake, move out early with your headlights still dipped. If you need to warn the other driver that you're there, flash your lights instead of using the horn. Return to full beam when you’re alongside the other vehicle. If you’re being overtaken, dip your headlights when the overtaking vehicle draws alongside you and keep them dipped until you can raise them without dazzling the other driver.  I I  136 Roadcraft - The Police Driver's Handbook Controlling your vehicle’s stability A vehicle’s stability is reduced when you brake, accelerate or steer because these actions produce forces that alter the vehicle’s weight distribution and balance, and reduce tyre grip. A vehicle may skid when one or more of the tyres loses normal grip on the road. See Chapter 5, page 91 The tyre grip trade-off. New vehicles are fitted with a growing range of active safety features to increase vehicle stability. There are two types of system; drive-assist features that drivers can choose to use, such as adaptive cruise control in-built safety features. This chapter briefly explains the principles of anti-lock braking systems (ABS), traction control systems (TCS) and electronic stability programmes (ESP). (Some manufacturers call this electronic stability control or ESC.) The principles of each type of system are similar but there are significant differences between manufacturers in how their particular system is activated and how it behaves. With rapid changes in technology, it’s vital that you refer to the manufacturer’s handbook to know which safety features are fitted to your vehicle, how to use them and what effect they’ll have on the vehicle. Be aware that many police and other emergency service vehicles may have a different specification from standard models. Safety features are there to protect you so, in non-emergency driving, they should be turned on. However, in some operational circumstances, and in some adverse weather conditions, you may want to consider turning off certain functions.  Chapter 7 - Maintaining vehicle stability 137. ’4 Attitudes to vehicle safety technology Research has shown that safety systems can give some drivers a false sense of security, causing them to become over-dependent on these features and take more risks than they would in a vehicle without them. Safety features can’t change the laws of physics - they don't make a vehicle perform better or increase a driver’s skill. If you're on the point of losing control of the vehicle, you’ve misjudged the situation. Safety devices can help you to regain control, but only if you understand the specific feature and know how to use it correctly. How active safety systems work Manufacturers are constantly seeking to improve vehicle stability with active safety features that can help safety and stability during braking, acceleration or steering. There are many more, but the active safety systems explained below are: anti-lock braking systems (ABS) traction control systems (TCS) electronic stability programmes (ESP). If an active safety system is fitted, you'll see an icon light up on the dashboard when you turn on the ignition or start the engine. If more than one device is fitted, they may be displayed separately or combined in a single warning light, When the system is activated, vehicles fitted with an active safety system will behave differently from vehicles without. Skid control in a vehicle fitted with one or more active safety systems will depend on the exact features fitted, Different systems intervene at different points and some models have a deliberately delayed point of intervention. If you drive different vehicles, you must take note of the manufacturer’s  138 Roadcraft - The Police Driver's Handbook A ii advice, and guidance in the driver’s vehicle handbook so that you fully understand how each vehicle is likely to behave ini extreme circumstances. Anti lock braking systems Almost all modern vehicles are fitted with ABS. This is an electronic safety device that adds to the conventionai hydraulic braking system by giving you some ability to steer during harsh or emergency braking. ® The foot brake applies the brakes to all four wheels at once, but ABS controls the braking appiied to individual wheels. It works by sensing when wheel IS slowing down and about to lock up. When this happens, ABS releases the brake on that wheel before it locks up fully. It re-applles the brake once the wheel starts to rotate again. The advantage of ABS is that it allows you to steer the vehicle under full braking power, because it prevents the wheels locking up. is nSdaTtr'® f rake pedal throughout. ABS may reduce or lengthen the ‘he stopping instance of the vehicle compared with conventional brakes on diffLnt oad surfaces but it allows the driver to retain some steering control [o] ABS can’t increase the grip of the tyres on the road fully prevent the possibility of the vehicle skidding. nor can it When the ABS activates, always ask yourself: ‘Could I have anticipated the hazard that caused me to brake so hard?’ \ /hen ABS is activated, y*ill fppi thn K u. " ®®® a earning light on the dashboard and I I feel the brake pedal vibrate or judder momentarily as the system nlodulates the brake line pressures. If you become aware that the ABS i IS 0 i ting in, you should learn from this and reduce your speed for the rest ^ e journey If you feel that you're experiencing brake fade, this may b|^because the system (combined with electronic stability systems) is anaging the braking to avoid the wheels locking up. Steering will affect this rr  A Chapter 7 - Maintaining vehicle stability 139 The effects of tyre grip trade-off will still apply and the system has to account for this effect. Emergency brake assist New vehicles now have emergency brake assist (EBA) as well as ABS. EBA increases braking pressure in an emergency situation. If you apply the brake with speed and force, EBA will cut in and fully apply the brakes until the ABS takes over to prevent the wheels locking up. Autonomous emergency braking Many modern vehicles are also fitted with autonomous emergency braking (AEB) systems. Find out what your vehicle is fitted with and what will cause it to activate. Traction control systems When you accelerate, it’s possible for the power transmitted to the driving wheels to exceed the amount of available tyre grip. This is more likely when moving off on icy or slippery roads, on a steep hill or accelerating out of a corner. This may cause the driven wheels to spin. Wheel spin reduces both the vehicle’s ability to accelerate and its stability. A traction control system works by controlling excess wheel spin on individual wheels. It applies independent braking to the spinning wheel. Some systems may also limit the wheel-turning power of the engine to increase tyre grip. TCS allows you to make maximum use of tyre grip, especially on slippery surfaces or where the friction of the road surface is uneven. An example is where one wheel can grip the normal surface but the other slips on ice or snow. If you activate the TCS, you’ll see a warning light on the dashboard. If traction control activates when you pull away from a standstill, reduce pressure on the accelerator to regain control of the steering.  140 Roadcraft - The Police Driver’s Handbook Note that if you switch the system off, the warning light will remain constant to advise you that you no longer have its assistance. Electronic stability programmes An ESP is an active safety system which incorporates conventional anti-lock braking and traction control systems. It’s designed to help vehicle stability by detecting when the vehicle is driven to the limit of its physical capabilities. There’s more variation between types of ESP than between types of ABS or TCS. Your vehicle’s handbook may explain what the manufacturer’s system does. Sensors at each wheel work in combination with a sensor that monitors the rotation and pitch of the vehicle - called a yaw sensor. Another sensor on the steering assembly detects the driver’s intended path. If these sensors detect that the vehicle isn't following the intended path, the system intervenes. It applies the brakes to individual wheels in order to correct understeer or oversteer and realign the vehicle. It’s therefore crucial that you steer in the direction you want to go. Most systems interact with the engine management system, reducing or increasing the engine power to the driven wheeis. Some also interact with the transmission system. ESP detects your intended path so it's cruciai that you steer in the direction you want to go, If you drive a vehicle beyond its physical capabilities, ESP doesn’t guarantee that the vehicle will remain stable and under control. It can’t defy the laws of physics.