TRCLC 16-11
Microsimulation of the Impact of Access Management Practices to Pedestrian Operations
Summary:
The study applied microsimulation to analyze the impact of access management (AM) to the operational performances of vehicles and pedestrians. A conceptual model was developed in VISSIM and VISWALK to examine the effect of access and signals density on different median types to the travel speed, travel time, delay and stopping. Access density, signal density, and presence of median were simulated in a scenario base analysis. The model scenarios shifted through changing both access density and signal density with no median, raised median and TWLT lane to provide interactions of arterial corridors in Nashville. The effect of access density on speed, delay and travel time was very vivid for the vehicles within the corridors showing speed decreasing with the increase in access density while delay increased and the number of stops increased. Additionally, as signal density increased, a decreasing pattern in corridor vehicle speed was observed. Pedestrian performances changes were less dramatic indicating that access density had a minimal effect on the pedestrian speed operations. The same trend was observed on signal density which affected pedestrian speed by a small decrease as signal density increased. The findings may provide useful understanding to state policy makers in implementing Access Management guidelines.
Problem:
Access management provides two major benefits to the transportation system; the preservation of highway capacity and improved safety (NCHRP Report 420, 1999). Of important is how access management practices affect pedestrian operations. In Tennessee, there is no published comprehensive study that has evaluated the impact of access management to the pedestrian operations. A quick survey in the Nashville metropolitan area showed no robust pedestrian access management guidelines or policies that are followed by the developers. In addition, oral interviews with some of transportation agencies and stakeholders revealed no or insufficient access management guidelines developed for different land uses.
Research Results:
Of many interesting observations, the following were some of the findings noted:
- There is significant change in travel speed as access density changes along undivided median roadways compared to raised median and TWLT segments.
- There is significant change in the number of vehicle stops and vehicle delays as access density changes along undivided median roadways compared to raised median and TWLT segments. Access density influences travel time more on undivided roadways than compared to other type of medians.
- The travel speed decreases along TWLT segments as signal density and access density.
- Delays and travel appear to be more sensitive to changes in signal density compared to changes in access density.
- Neglecting the median type, changes in the access density and signal density does not affect much the average pedestrian speeds.
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Pedestrian travel times are lowest along raised median areas compared to undivided and TWLT counterparts.
