Implications of changing the left turn rule

Anna Wilkins, a Principal Transportation Engineer in TDG’s Hamilton office, was recently invited to present to the NZ Transport Agency (NZTA) Waikato/BOP Traffic Management Liaison Group (TMLG) about implications of changing the New Zealand left turn rule on intersection performance.

Anna presented to the group about her research project that used S-Paramics microsimulation modelling to assess a range of real intersections and transport networks before and after the rule change.

Some intersection types are particularly susceptible to deteriorated performance following the rule change. Others can be expected to improve. Whilst this depends on each intersection’s layout, volumes and location in the network, the research found that intersections can generally be classified into one of four groups.

Anna’s presentation summarised the main characteristics of these groups with typical examples that road controlling authorities should be aware of as the rule change approaches in March 2012.