TRAFFIC LIGHTS

Evening Post, Volume CXXVIII, Issue 49, 26 August 1939, Page 10

TRAFFIC LIGHTS

FIVE-WAY CONTROL

CLEAR IN OPERATION

fTO START ON MONDAY

The new traffic control lights at the intersection of Wakefield Street. Jervois Quay, and Taranaki Street will be put into service on Monday. Drivers will find the control clear in practice, though the half-dozen standards, carrying back-to-back sets of lights, and in two cases three sets, look difficult with the lights out. The clear operation is reached through the angles and the hooding of the lights, so that drivers approaching the intersection can see only the signals that are good for them. Nevertheless the diagrams and details which follow should be studied, so that the control will be understood from the first.

There are only three phases. During the greater part of the day the through run from Jervois Quay to Wakefield Street will be the most heavily trafficked, but at certain times the east and west traffic in Wakefield Street gains in volume, with, at all times, solid traffic turning to and from Taranaki Street. . The point to be kept in mind is that .the lights which concern the driver are those right ahead, and, as will be seen from the details below each of the phase diagrams, there may be more than one green ahead. Pedestrians must use the marked crossing and obey the lights equally with vehicular traffic. WALKERS AND TRAMS. Provision is made for pedestrians by the raised islands and also by lights for the main crossing over Taranaki Street. "Cross now" lights have been added to the pillar at the Wakefield Chambers corner, but not at Lyson's corner, where the red, amber, and green traffic lights are clearly visible at the end of the marked crossing. There is a good deal of pedestrian traffic each morning and afternoon between the petrol station and Lyson's corner, when women and girls are on their way to and from work in Cable Street No special lights have been erected for this crossing so far: In place of road surface pads, trams running in Wakefield Street will operate contacts in the overhead wiring and will be subject to the same .'light signal control. For a" day or two traffic officers will be stationed at the intersection till traffic gets into the hang of the lights, but no difficulty is anticipated. During . the past week evening trials were made from 7 o'clock onwards, when there was a fair amount of theatre traffic on the roads, and though no warning had been given that the control would be in. operation it worked generally very satisfactorily. The system is capable of great flexibility, and adjustments may still be made according to its operation under heavy traffic. ALLOWANCE FOR FAST AND SLOW. As at the Queen's Wharf gates, traffic will control itself, by making con- ' tacts through the road pads, with a general oversight and master supervision in the control box, so that no ; vehicle on a lesser used roadway may be too long delayed. The control does" more than that; it actually distinguishes between fast and slow vehicles. After a pad has been pressed and the way opened ahead the mechanism will hold the green until a contrrjry impulse is given from another pad. but if, just as the light is about to change, another vehicle follows on the green way the control will extend the green for a sufficient time to let the car or what it is across. A car doing thirty miles an hour needs only a fraction of the time needed by a tractor and trailer, and a clever piece of equipment in the control box looks after that. The fast car zips over the pad, and the tractor gives it a good squeeze, and according to the time the pad is depressed so the green light may be extended. The detail of this section of the control is too technical to describe simply; its essential elements are a condenser of large capacity and a neon lamp. The potential in the condenser gradually builds up to a setj pressure and then flashes off through the neon lamp, the extent of discharge being determined by the length of pressure on the pads and the completeness of the discharge controls, through

a series of relays, the length of time the signals are held.

The system is coupled to the Central Fire Station by a ..pecial line and if engines are bound over the intersection the station officer can override the pad and master control by pressing a button; all lights are then held at red for a sufficient time to allow the engine to clear the crossing.

A technical man could write half a page about the details of equipment and adjustment. That does not particularly interest the man who uses the intersection. He is more concerned with the simplification of detail to practical guidance. That is the job of the technical man, and in this instance, as far as the tests have gone, he has made a real success of it.