ブックタイトルマツダ技報　2012 No.30

概要

マツダ技報　2012 No.30

No.30(2012)マツダ技報3. Describing the taskFig.1 Different Critical Pathways to Enter Blind Spot AreaIn parallel to this task, the driver must judge the trafficsituation ahead: how much time is left until the laneends or the car in front be reached.The criticality of this situation rises with high speeddifferences of the rear approaching vehicle compared tothe ego-vehicle and its speed difference to a vehicle infront or the distance to the end of lane ahead. In Europehigh differential speeds occur on highways wherepassenger cars typically travel at 130km/h (in Germanypartly unlimited). Trucks and merging traffic from otherroads drive at 80 to 100km/h, so that aΔV of up to50km/h can occur frequently.2.3 Accident causation research and expected effect ofRVM to accident occurrenceIn Europe various accident statistics on country andEU level exist that count the number of accidents andoften assess the severity and causation. The most recentGerman official accident statistics of Destatis (1) from2010 show that around 4.4% of accidents with injuryhappen laterally among cars that travel in the samedirection. A“German In-Depth Accident Study”databasecalled GIDAS (2) has analyzed about 20,000 accidentswith injury in detail and with full reconstruction. GIDASreports about 4.8% lateral accidents, the BritishTransport Research Lab (TRL) (3) about 5%. Thesevalues need to be corrected by some factors such as carsthat did not pursue a lane change but e.g. lost control.Nevertheless it is important to work on these numbers inorder to reduce fatality, injury and damage. Byconsidering all factors available and using the GIDASDatabase as the information source of highest accuracy,it is possible to extrapolate that annually about 560 livescould be saved in the EU through general introduction ofRVM technology, 2,100 severe injury accidents and about8,300 slight injury accidents could be avoided. Thenumber of accidents with just damage are at least 2magnitudes higher.3.1 The process of a proper lane change and the task ofavoiding its accidentsAs already described above, lane change typicallyshould start with a look into the mirror and over theshoulder. (4) In reality drivers often neglect the shoulderview based on carelessness, discomfort or age basedphysical impairment. This can lead to undetectedvehicles in the blind spot area. Also it is reported thatbased on distraction or other mental occupation driverslook into the mirror or over the shoulder, but do notidentify an approaching vehicle.(5) Even if a vehicle getsdetected by the driver, the judgement of the relativespeed difference can be very difficult, if the other vehicleis extremely fast, has a colour that contrasts little to theroad environment (e.g. dark grey) or weather conditionslike rain mask it.The task of a safety device that supports to avoid lanechange accidents can be described with the followingstatements:? Vehicles in the blind spot area should be confirmedto the driver, even, if he does not detect them basedon above mentioned reasons.? Vehicles that will reach the lateral position to theego-vehicle on the adjacent lane within a definedshort time shall be notified as well.? Should the driver of the ego-vehicle still indicate hislane change intention, then a warning should beplaced, convincing the driver to abstain from lanechange.3.2 The critical area around the vehicleThe above described tasks imply the detection ofvehicles in an area, left and right and behind of thevehicle. The blind spot area is depending on the driverseating position and the resulting side mirror aiming. Tobe sure to detect cars in all possible blind spot geometries,Mazda decided that the detection area should stretchlongitudinally from the centre of front side window backto 10m behind the vehicle. The lateral detection shouldreach from the vehicle to a distance of 3.5m, coveringalso wide highway lanes. For defining the so-calledclosing area of approaching cars, the relative speeds ofvehicles on different lanes and necessary reaction timefor driver of the detected vehicle need to be considered.This lead to the understanding that this zone shouldstretch 50m behind the blind spot detection zone.―171―