On-ramp merge capacity in Finland

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Insinööritieteiden korkeakoulu | Master's thesis
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Managing Spatial Change, Urban Engineering
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Master's Programme in Transportation and Environmental Engineering
This research examined the macroscopic characteristics of traffic flow on on-ramp merging segments. The methodology of the new U.S. Highway Capacity Manual (HCM 2010) was used as a framework for the analysis. Following the HCM 2010 method, density was used as the measure of level of service (LOS). This research was intended to calculate the capacity and optimum density on on-ramp merging segments with Finnish traffic flow. Measured data has been gathered in 2013 from six on-ramp merging areas in Helsinki Metropolitan Area. Traffic flow data was collected from six recording cameras on each site located before and after the merging of vehicles. The data used in this research excludes disturbances such as accidents, roadwork, and bad weather. The HCM model’s parameters were estimated by the measured data. The measured data was used to estimate average speed, traffic volume, and traffic density. The examination was then completed in two parts. The first part consisted of analysis of empirical macroscopic dataset. The second examination consisted of estimating capacity and optimum density from this dataset following the HCM 2010 procedure. The six on-ramp merge locations were analyzed to estimate the maximum flow i.e. capacity and optimum density, after which unstable flow occurred. In most of the locations higher upstream flows were identified as the major cause of speed drop and congestion. Overall analysis of the data, led to the conclusion that the 31 vehicle per km per lane could be suggested as the optimum density value. The data suggested that a maximum output capacity of 4,400 pcph be adopted for four-lane single-lane on-ramp merge areas in Finnish traffic conditions. This value represented the average of the all six sites for which 2-hour data was used.
Luttinen, Tapio
Thesis advisor
Enberg, Åsa
Ojala, Virpi
on-ramp merging, capacity, optimum density, macroscopic traffic flow
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