1419563 Detecting passage of road vehicles SIEMENS AG 16 Feb 1973 [17 Feb 1972] 7655/73 Heading G4Q A traffic measuring system for use on a road, such as a motorway, having two lanes F1, F2 in which traffic moves in the same direction P comprises respective detectors 1, 2 at at least one measuring position A and a storage and averaging circuit which forms an average time interval between vehicles on each lane, and means for deriving lane comparison data. As shown, further detectors 3, 4 are provided at a second measuring position B. The output of each detector passes to a counter ZM in the form of pulses. Each time a vehicle is detected, the counter is reset to zero and its count simultaneously transferred to an averaging device MW1. Here, successive inputs are averaged and the results stored in registers R1, R2. A differencing device in device MW1 forms the difference between the old average Za of time intervals and a new interval Zn. This difference is multiplied by a factor α and then added to the contents of the registers R1, R2. Simultaneously, the difference (Zn-Za) is fed to a squaring device PB1 and thence to a second averaging device MW2 connected to registers R3, R4 in a manner similar to the device MW1 and registers R1, R2. The contents of registers R2, R4 (i.e. Zn and Sn) are supplied to a multiplier PB2 upon the production, at 60 second intervals, of sampling pulses. The circuit so far described is duplicated so that each detector 1-4 provides signals processed as above. The output a 1 from device PB2 is applied to a quotient-forming device QB together with a similar output a 2 derived from detector 2. The quotient thus formed passes to another averaging device MW3 connected to a register R5 to produce and store an average Kn(A) of the quotients derived from signals obtained at position A. A similar average Kn(B) from signals obtained at position B is fed, simultaneously with the average Kn(A) to a differencing device DB1. For normal traffic flow, X A # X B and Y A # Y B where whereas, for traffic flow with an obstacle Hi present, Z B3 > Z A1 and Z B4 < Z B2 (because of density changes due to lane swapping) and, thus, and S B3 > S A1 and S B4 < S A2 (because S B3 corresponds to free-moving, low density traffic and S B4 to restricted, high density traffic) and, thus, and hence The difference (Kn(A)-Kn(B)) is fed to an analyser AW from which a "zero" output shows no restriction to traffic flow. Moreover, for an individual measuring position, say the position A, a difference between the quotients Kn, Ka is formed by unit DB2 between sampling intervals to show the degree of change of restriction with time. The output of the system may be used to control traffic signs.