WHO'S WHO IN ROADS
N1 widening underscores the value of planning
Completion of the additional lanes, shoulders and concrete median barrier. The original 20 mm UTFC layer was replaced with a 25 mm UTFC layer
Over past decades, the N1 (TR9/1) connecting Cape Town’s Nor thern Suburbs has progressively evolved into a superhighway. The most recent inter vention is the widening of an approximately 5 km section between Jip de Jager Avenue and Old Oak Road from a four- to a six-lane dual carriageway along with a range of associated works. The demolition operation started on a Friday night and included both the demolition and removal of debris from the roadway. The road was reopened to traffic on Saturday afternoon – less than 24 hours after demolition began
The original fourspan Old Oak bridge consisted of a beam and slab deck supported on three piers and two abutments. The contractor elected to demolish the bridge using large excavators. A sand layer was placed on the existing roadway to protect it from falling debris
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IMIESA April 2021
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ed by the Western Cape Department of Transport and Public Works, SMEC South Africa was appointed in 2013 for the full scope of professional services. This ranged from project management, planning (including traffic modelling and analysis), detail design and procurement, to contract administration, supervision and close-out. “When design work commenced in 2013, in excess of 120 000 vehicles were already using this route daily, making it one of the highest-trafficked roads in the province,” explains Michael Hendrickse, chief engineer: Geometric Design, Western Cape Department of Transport & Public Works. “This also meant that when the 36-month construction programme started in 2016, traffic flow disruptions had to be kept to a minimum. For this reason, key phases were often completed at night, such as asphalt resurfacing.” The City of Cape Town’s Regional EMME Model was used to forecast traffic demand volumes based on a 20-year design horizon post implementation. This was further refined by employing a microscopic transportation modelling simulator to calculate anticipated travel times and average speeds during the morning and afternoon peak periods. “The model that we used assumes a residential growth of 50% or 500 000 dwelling units in 20 years – i.e. by 2032,” says Hendrickse. “It also incorporates a modal shift towards public transport and takes into
