Intelligent speed adaptation

Intelligent speed adaptation (ISA), also known as alerting, and intelligent authority, is any system that ensures that vehicle speed does not exceed a safe or legally enforced speed. In case of potential speeding, a human driver can be alerted, or the speed reduced automatically. Intelligent speed adaptation uses information about the road to determine the required speed. Information can be obtained from knowledge of the vehicle position, taking into account speed limits known for the position, and by interpreting road features such as signs. ISA systems are designed to detect and alert a driver when a vehicle has entered a new speed zone, or when different speed limits are in force according to time of day and conditions. Many ISA systems also provide information about driving hazards (e.g. high pedestrian movement areas, railway crossings, schools, hospitals, etc.) and limits enforced by speed and CCTV cameras at traffic lights. The purpose of ISA is to assist the driver to maintain a safe speed. Research has found that, in urban areas, the number of crashes causing casualties is doubled for each 5 km/h (3.1 mph) over the limit. Enforcing speed limits strictly enough to eliminate slight overspeed is difficult; it is proposed that ISA will assist with this. It is also argued that speed limits need to be properly set as those too low will equally cause issues. Drivers maintaining speeds significantly below a posted limit have been shown to have an increased accident risk compared to those nearer the limit (including those slightly over the limit). The two types of ISA systems differ in that passive systems simply warn the driver of the vehicle travelling in excess of the speed limit, while active systems intervene and correct the vehicle's speed to conform with the speed limit. Passive systems are generally driver advisory systems: They alert the driver to the fact that they are speeding, provide information as to the speed limit, and allow the driver to make a choice on what action should be taken. These systems usually display visual or auditory cues, such as auditory and visual warnings and may include tactile cues such as a vibration of the accelerator pedal. Some passive ISA technology trials have used vehicles modified to provide haptic feedback by making the accelerator pedal stiffer when appropriate to alert the driver. Most active ISA systems allow the driver to override the ISA when deemed necessary; this is thought to enhance acceptance and safety, but leaves a significant amount of speeding unchecked.