Journal of Transportation Engineering · 2003 · 51 citations · 6 references
EngineeringCivil EngineeringTransportTransportationTransportation EngineeringFlow MeasurementHighway Capacity AnalysisTraffic EngineeringTraffic Flow AnalysisTraffic Flow ManagementTraffic Flow TheoryFlow Rate CharacteristicsFlow Velocity MeasurementsHighway Performance MeasurementHighway Traffic FlowTime Interval MeasurementTraffic Flow Rate
Traffic flow rate, the hourly rate of vehicles passing a point, is a key transportation metric, and the measurement interval used to compute it influences its stability, although the Highway Capacity Manual recommends at least 15‑minute intervals and researchers have noted instability with shorter intervals, there is no quantitative understanding of the effects of intervals shorter than 15 minutes. The study aims to quantify how measurement interval length affects freeway traffic flow rate stability using nearly 30,000 measurements. The authors collected and analyzed nearly 30,000 flow rate measurements from multiple freeway locations to assess the impact of measurement interval. The study found that stable freeway flow rates can be calculated with intervals as short as 10 minutes, and adding 2 minutes to any interval yields statistically significant improvements in stability.
Traffic flow rate, the equivalent hourly rate of vehicles passing a point during a given time interval, is a fundamental measure of traffic status that plays a critical role in many aspects of transportation engineering. The time interval used in measuring the flow rate, defined as the measurement interval, is influential in the characteristics of flow rate measures. In fact, the Highway Capacity Manual recommends that transportation engineers use a minimum of 15-min measurement intervals in order to ensure "stable" traffic flow rates. In addition, numerous researchers have commented about the lack of stability of flow rates resulting from short measurement intervals. However, there is not a quantitative understanding of the impacts of short (less than 15 min) measurement intervals on traffic flow rate. This paper presents the results of a study using nearly 30,000 flow rate measurements collected at multiple freeway locations to quantify the impact of measurement interval. It was found that stable freeway flow rates may be calculated using measurement intervals as short as 10 min, and that statistically significant improvements in stability can be achieved by adding 2 min to any measurement interval.
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