Vehicle collision alert system

An apparatus for determining an excessive speed approach of a vehicle to an object in front of said vehicle, comprising:

• a normalized time rate of change detector for determining a normalized time rate of change of a visual angle, (1/.theta.).multidot.(d.theta./dt), for said object as viewed from said vehicle, the normalized time rate of change detector including means for measuring a distance D of said vehicle with respect to said object, means for measuring a relative speed Vr of said vehicle with respect to said object, and means for dividing the measured relative speed Vr by the measured distance D to calculate the normalized time rate;
• and
• an indicator for producing an indication of the excessive speed approach based upon the normalized time rate, said indicator including means for producing a first alarm to indicate a recognition of an excessive approach of said vehicle to said object when the normalized time rate exceeds a first range of 6%.+-.1.1%, said first range corresponding to a driver's recognition of an excessive approach of said vehicle, and for producing a second alarm indicating danger of a rear-end collision when the normalized time rate exceeds a second range of 12%.+-.2.2%, said second range corresponding to a driver's recognition of danger of a rear-end collision.