GB1004415A - Improvements in or relating to the determination of road traffic conditions - Google Patents

Abstract

1,004,415. Road traffic measurements. DECCA Ltd. Sept. 12, 1961 [June 13, 1960], No. 45100/61. Divided out of 1,004,414. Heading G4Q. [Also in Division G1] Apparatus for providing an output representative of the mean speed of road traffic comprises means providing a first electrical output representing traffic congestion at a point, means providing a second electrical output representing rate of traffic flow at said point, and means responsive to said first and second outputs for determining the ratio between the congestion and the flow. As shown, Fig. 1, passage of a vehicle wheel over a pad 10 embedded in a road surface 11 closes contacts 12 in series with a power source 13 to produce a pulse of duration inversely proportional to the speed of the vehicle. A succession of such pulses is fed to an integrator 14 controlled by a timing device 15 to produce an output representing congestion which may operate an indicator 16 or be recorded or fed to a computer &c. The pulses are also normalized at 18 into pulses of uniform duration which are fed to a second integrator 19, also controlled by device 15, to produce an output representing rate of traffic flow, which may be indicated at 20 &c. The outputs from integrators 14, 19 are also supplied to a ratio determining device 21 which produces an output representing mean speed which is fed to indicator 22. In a modification, Fig. 2 (not shown), timing device 15 is rendered unnecessary by the use of leaky integrators comprising a high gain amplifier with an input resistor and a feedback circuit comprising a capacitor shunted by a high impedance resistor. Separate vehicle sensing elements may be used in different lanes of a road, and the pulses may be transmitted to remote integrators by modulation of a carrier frequency. Specification 1,004,413 also is referred to.