More miles per gallon . . . or rather, kilometers per liter. That's been the objective of many programs here at the General Motors Research Laboratories. One of these concerns urban traffic. Our scien tists have conducted studies to determine which traffic variables have the greatest effect on gasoline con sumption, and how much fuel could be saved through improved traffic flow. They began by driving instrumented cars in traffic at different levels of congestion. From a detailed multivariate analysis of the data, they found that a car's fuel consumption in city traffic was related simply and linearly to average trip time (see equation). Confirmed in traffic experiments, this rela F = A + BT tionship suggests that (valid up to ~ 60 km/h) drivers would use less F = fuel consumed per unit distance fuel if traffic conditions A = constant related to average permitted higher aver vehicle mass Β = constant related to average age trip speeds, thus idle fuel flow rate Τ = average travel time per unit shortening trip times. distance What order of fuel savings could be expected? An analysis was made of trip-speed data collected by GM in Chicago, Denver, Detroit, Los Angeles, New York, San Francisco, and Washington, D.C. Two results: If traffic flow improved so no trip averaged less than a modest 24 km/h (15 mph), a 2.5% fuel saving would result. If the average of all trip speeds equaled that attained in uncongested traffic, 13% would be saved (see graph).
Mapping fuel savings through improved traffic now.
DISTRIBUTION OF SPEEDS IN SEVEN CITIES C D = Observed § • = Calculated Distribution Distribution for Uncongested Traffic
0-10 110-20 I 20-301 30-40140-50 150-601 60-70 170-80 180-90190-1001 Average Trip Speed Ranges (km/h)
Our scientists also developed and validated a computer model to predict travel times throughout a complicated road network. It enables researchers to estimate fuel savings from traffic engineering improve ments, car-pooling, staggered work hours, etc. Traffic research: Driving toward better fuel economy and a more pleasant trip for you.
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We currently have openings for Ph.D.s in engineering or the physical mathematical or biomedical sciences. If interested, please send your resume to: GMR Personnel, Dept. 1111. An Equal Opportunity Employer.
General Motors Research Laboratories Warren, Michigan 48090
