Patent GB-1424350-A (GB)
Title: System for controlling traffic in a network having a number  of fixed points interconnected by paths
IPC: G08G1/00
Filed: 1972-12-29
Abstract: 1424350 Traffic &c. control HARADA DENGYO CO Ltd 29 Dec 1972 [30 Dec 1971] 60102/72 Heading G4A A system for use in controlling the passage, e.g. of motor vehicles, through a route network having n interconnected points includes a means for establishing an n x n matrix M for the network, the matrix elements m i,j  for i#j being 0 when a direct path between point i and point j is not available and 1 otherwise, and being 0 for i = j, means for establishing an n dimensional vector X whose elements x i  are 1 where the ith point is of a predetermined kind (e.g. an exit) and 0 otherwise, means for calculating the matrix products (M<SP>l</SP>) (where M<SP>2</SP> = M.M) the elements m<SP>l</SP> i,j  of which are 0 for i = j, are 1 when calculated as #1, and are 0 otherwise, and means for calculating successive products M<SP>L</SP>.X for L = 0, 1, 2,... to form for each such product a series of results a i,L  where i = 1, 2 ... n, whereby the first calculated result a i,L  # 1 for a given i indicates that the ith network point is the Lth point from a point of the predetermined kind (exit). General-.The network matrix M for the network of Fig. 1 is:- and the exit vector X is:- X = (1, 1, 0, 0, 0). Level 0 points in the network, i.e. exits, are given directly by X, in general terms X.M‹ (where M<SP>0</SP> is the identity matrix). The ith point is level 1 if m i,j  = 1 and the jth point is level 0. The levels of the remaining points are determined by determining the successive products M<SP>L</SP>.X, each product being a series of results a i,L  for i = 1, 2...n. For each a i,L  #1 the ith point is of level L unless previously found to be of lower level. Certain elements in a matrix M<SP>L</SP> may have values >1 and indicate, by their value, the number of paths available between points i and j, via intermediate points. It is however sufficient to determine whether a path between points i and j exists so that all elements #1 are set equal to 1. The calculations proceed until the levels of all points in the network have been determined. The arrangement may be used for road traffic control, a computer being used to perform the calculations and the matrix and exit vector being updated as appropriate in response to changing conditions using sensors in the network, e.g. to detect blockage of a previously available path. Traffic signals may be provided in the network to signal available routes, e.g. the shortest route to an exit. Details.-In the event of a change of status in the network signals from the sensors are used to derive an n bit words, one bit per point, which are written, in a series of cycles, into one, P, of two shift registers P, Q. The number of network points identified by each word is determined and if two are identified one is written into Q, the other remaining in P, whereas if only one is identified it remains in P, Q being filled with " l's ". The contents of registers P and Q are used to update the matrix. The matrix calculations are performed using two sets of n, n-bit circulating shift registers, one set containing a matrix with rows transposed to columns and vice versa to allow the calculations to be performed by circulating the two register sets through a calculating device synchronously.