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Braking distance refers to the distance a vehicle will travel from the point when its brakes are fully applied to when it comes to a complete stop. It is primarily affected by the original speed of the vehicle and the coefficient of friction between the tires and the road surface, [Note 1] and negligibly by the tires' rolling resistance and vehicle's air drag.
d MT = braking distance, m (ft) V = design speed, km/h (mph) a = deceleration rate, m/s 2 (ft/s 2) Actual braking distances are affected by the vehicle type and condition, the incline of the road, the available traction, and numerous other factors. A deceleration rate of 3.4 m/s 2 (11.2 ft/s 2) is used to determine stopping sight distance. [6]
The two-second rule is useful as it can be applied to any speed. Drivers can find it difficult to estimate the correct distance from the car in front, let alone remember the stopping distances that are required for a given speed, or to compute the equation on the fly. The two-second rule provides a simpler way of perceiving the distance.
For heavy duty commercial vehicles it is recommended 4-6 seconds following distance for speeds under 30 mi/h (48 km/h), and 6-8 seconds following distance for speeds over 30 mi/h (48 km/h). [9] Rear-end collisions are the number one type of traffic collisions .
Headway is the distance or duration between vehicles in a transit system. The minimum headway is the shortest such distance or time achievable by a system without a reduction in the speed of vehicles. The precise definition varies depending on the application, but it is most commonly measured as the distance from the tip (front end) of one ...
0 to 100 km/h (0 to 60 mph) seconds seconds seconds acceleration: lower is better 0 to 100 to 0 mph seconds seconds seconds acceleration and braking: lower is better formerly common in British publications Autonomy: miles miles kilometers comfort, safety, economics, range higher is better Autonomous means self-governing. [1]
Should the driver fail to react, the Pre-Safe Brake triggers autonomous vehicle braking. Pedestrian detection is active up to about 72 km/h (45 mph), and can reduce collisions with pedestrians autonomously from an initial speed of up to 50 km/h (31 mph). [44] A radar sensor in the rear bumper monitors the traffic behind the vehicle.
Emergency stopping distances can be shortened, reducing the likelihood of accidents – especially the common "nose-to-tail" incident. An electronic system designed to recognise emergency braking operation and automatically enhance braking effort improves vehicle and occupant safety, and can reduce stopping distances by up to 70 ft (21 m) at ...