civil engineering - roads
N24 CARRICK ON SUIR ROAD SCHEME VISUM TRAFFIC MODEL
O’Connor Sutton Cronin & Associates (OCSC) was commissioned by South Tipperary County Council (STCC) to advance the N24 Carrick on Suir Bypass Road Improvement Scheme through to Phase 4 of the National Roads Authority (NRA) National Project Management Guidelines. The N24 is a strategically important National Primary Route which runs from Limerick to Waterford, passing through Tipperary, Cahir, Clonmel and Carrick on Suir and is significant in a local, regional and national context.
The Study Area for the route is approximately 150sq.km. The section of the N24 network under consideration as part of the traffic model development is approximately 17 kilometres in length; commencing approximately 4km East of Carrick OnSuir on the Piltown Bypass to a point west of the N24/N76 junction at Kilheffernan Cross where it is proposed to join with the eastern terminal of the Clonmel Bypass.
As part of the traffic data collection, major traffic surveys were carried out including an Origin – Destination Survey along with Junction Turning Counts, Road Side Interviews, Automatic Traffic Counts, and Journey Time Surveys. The strategic modelling tool VISUM was then used by OCSC to develop a traffic model for the study area. A traffic model in VISUM consists of transport supply data and travel demand data. The demand side consists of one OD matrix per time of day (am/pm peak) and demand segment (LGVs, HGVs) built around Road Side Interviews (RSIs) and local knowledge about the study area. The influence of the Carrick on Suir Bypass on all existing road users either on or crossing the N24 is the key issue in the analysis. Five route options were considered for the evaluation of the traffic impact and to estimate percentage of traffic shift to the proposed bypass from existing road network. Economic assessment of the route options for the Bypass was carried out using COBA software. COBA compares the cost of providing road schemes with the benefits derived by road users (in terms of time, vehicle operating costs and accidents), and expresses the results in terms of monetary valuation.
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