Speed limits are established based on the type, geometry, and conditions of the road, the category of vehicles that circulate on it, and traffic conflicts in the surroundings. It is worth mentioning that adverse weather conditions also interfere with the choice of safe speed to travel.The most important thing is to remember that a safe speed to travel is associated with the ability to brake if something unexpected is in the driver’s path and also looking out for road bump.
The braking distance is the minimum distance a vehicle travels to come to a complete stop before hitting an obstacle. But the braking of a vehicle depends on the driver’s perception time, which is the interval between seeing the obstacle and making the decision to brake (this time can vary between 0.7 and 1.0 seconds), combined with the reaction time of the driver, which is the difference between the moment when the driver decides to brake and the moment when he activates the vehicle’s brake system. Studies indicate that this time varies from 0.5 to 1.0 seconds.
Even though it is challenging to identify the factors contributing to traffic accidents clearly, studies indicate that at least 1/3 of crashes involving death involve speeding. Excessive speed (exceeding the limit) or inappropriate speed (for the weather and road conditions) are the single factors that most contribute to traffic deaths since, in addition to being the cause of many accidents, they contribute to the severity of these accidents. In addition to increasing braking time, excessive speed increases the probability that the driver will lose control of the vehicle, reduces the ability to anticipate dangers, and confuses other traffic actors as to the actual speed of the vehicle.
Studies provide direct evidence that driving just 5 km/h above average in urban areas and 60 km/h above average in rural areas is enough to double the risk of an accident. Evidence also indicates that moderate speed (10 to 15 km/h over the limit) contributes more significantly to traffic accidents – compared to the contribution of more extreme speeds – as it is a very common behavior.