Inclement weather and traffic flow at signalized intersections - Case study from northern New England

Gridlock along arterial systems in New England is often the result of adverse weather conditions, which can render the normal signal plans unsuitable. The current study has two main objectives: (a) to assess the impact of inclement weather on traffic flow parameters at signalized intersections in northern New England and (b) to evaluate the likely operational benefits of implementing special timing plans for inclement weather conditions. A signalized intersection in Burlington, Vermont, was selected, and at least 30 h of videotaped data were collected over a period of 3 months. The weather and road surface conditions were categorized into six different classes, and values for the saturation headways and start-up lost times were collected and statistically analyzed. A signalized collector was then selected as a case study for evaluating the likely benefits of developing special timing plans for inclement weather. Optimal signal plans were developed for the corridor for the six different weather conditions. The likely benefits of the special plans were then determined by comparing travel conditions under the optimal inclement weather timing plans with conditions assuming the optimal dry-condition plan would remain unchanged. The study reveals that inclement weather has a significant impact on saturation headways, particularly once slushy conditions start. Start-up lost time, however, does not appear to be significantly affected by inclement weather. The study also shows that there are benefits to be expected from implementing special signal plans for inclement weather.