As we often drive a car at night under the driving situation that only the use of low beam in headlamps is permitted, despite driver's desire to use high beam, photometric improvement in the low beam is considered to be necessary in order to improve driving visibility. Most drivers wish to have improved low beam which is capable to see a far distance, while they demand not to have dazzling light distribution on opposing cars. A means to see a far distance is to increase the lamp intensity or an upward looking lighting line. In the latter case road surface near the vehicle becomes dark. For that reason an increase of lamp intensity is selected in order to see a far distance. But, as we know, it is the glare that affects driver's visibility which causes an increased serious problem.

Hence the threshold level of the glare is examined based on field tests finding a tolerable level of discomfort due to the dazzling and target visibility. Further, increase of visibility distance is examined when the headlamp intensity is increased to threshold level of the glare.