Speeding •Up Traffic Flo
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Investigations by the Road Research Laboratory Reveal a Continua] Worsening of Conditions in Central London: No-parking Regulations Provide Some Relief: Widespread Disregard of Speed Limits by Commercial Vehicles T"probable effect of reducing the flow of taxis by,100 per hour would be to .increase the average speed of traffic in London by 0.5 m.p.h., and by. removing a similar number of heavy goods vehicles, by 3.5 m.p.h. Observa. lions made at pedestrian crossings in the' suburbs show that zebra crossings. impede traffic flow to an extent 2/ times greater than ordinary crossings.
• These and many other interesting figures were given by Dr. G. Charles B.Sc., Ph.D., F.Inst.P., of the Road Research Laboratory, to members ' of' the Institute of Road Transport Engineers inTondrin yesterday.
Traffic figures obtained on 36 miles. of -main :road— in Central London between 1947 and 1952, showed that: there Were about twice as many: vehicles engaged On Corninercial transport as • there were private cars. The average journey speed was 11.3 m.p.h.
Decline in Taxis Taxi traffic had shown a decline of about 20 per cent. between/1950 and 1952. Heavy goods traffic had also decreased, whereas light goods vehicles., had increased. Whilst journey speeds on The Mall showed an: average.of 21 m.p.h., the figure for:Oxford Street was 5.5 m.p.h. and for .Piccadilly 8.3 m.p.h.
A decrease in the Sneed of . traffic flow of about 4 per eerit. resulted from, the use Of 8-ft.-wide buses.: The, Observations were made in 1950, in Notting Hill Gate, ,Shaftesbury Avenue and Threadneedle Street. .
• Since trams ,were withdrawn, journey speeds had ,increased by 12 per, Cent., despite an increase in the amount of traffic. This improvement had repercussions in areas not affected by the removal of trams, the increase in .sueh districts . being 7 per cent. Accidents on routes. from .which trams had been
removed had decreased. •
Peak-hour Speed Despite 'an increase of 10 per cent. in traffic flow atpeak hours,' journey speeds were only 3 per cent. slower. This Was probably accounted -for by the redaction inthe number of goods vehicles on the road between 5 p.m.
and 6 p.m. .
Restrictions placed on parking in certain areas had resulted in the speeding up of traffic flow to the extent of 2.5 per cent. in Central London, and
3.8 per cent. in the suburbs. Controlled intersections were among the most important causes of traffic delay in towns.
On the survey routes followed in London in 1952, there were aboot five intersections per mile and the average time stopped per mile of journey at these points was about minutes. A method which had been adopted to reduce delays was to link traffic signals so that when the first showed green the others on the same route would change at timed intervals to provide a theoretically clear run.
Examples of linked systems were to be found in Oxford Street, Edgware Road and iviarylebone Road. Although improvements had been noted since the linked System had been adopted, it did not provide the complete answer to unimpeded traffic flow.
Delay at traffic signals was largely dependent upon the rate at which traffic could be discharged while the light was green. This discharge rate for normal mixed traffic was about 1,250 vehicles per hour per 10 ft. of width. A parked vehicle on the approach to an intersection decreased the discharge rate by 20 per cent.
In the area north of the Thames between Westminster and the City, the average number of vehicles parked during business hours was 4,000 per mile; the intensity varied from about 2.000 in parts of the City to 8;000 in Mayfair. Observations made over an area of approximately +-mile radius in the West End of London showed that between 1951 and 1953 the extent of parking had increased by 44 per cent.
On open roads nearly 90 per cent, of coaches exceeded their legal limit of 30 m.p.h., as did over 60 per cent. of goods vehicles subject to the same limit. In the case of heavy goods vehicles, only 2 per cent, observed the speed limit of 20 m.p.h.