Traffic Signal Optimization to Improve Sustainability: A Literature Review

Abstract

Optimizing traffic signals to improve traffic progression relies on minimizing mobility performance measures (e.g., delays and stops). However, delay and stop minimizations do not necessarily lead to minimal sustainability measures (e.g., fuel consumption and emissions). For that reason, researchers have focused, for decades, on integrating traffic models, signal optimization models, and fuel consumption and emissions models to minimize sustainability metrics while keeping acceptable levels of mobility metrics. Therefore, this paper reviews, classifies, and analyzes studies found in the literature regarding optimizing sustainable traffic signals. This paper provides researchers with a good starting point to further develop solutions which can address sustainable traffic control. To achieve that, this study details the most notable sustainable signal timing optimization studies from six perspectives: traffic models, fuel consumption and emissions models, optimization methods, objective functions, operating conditions, and reported sustainability savings. Outcomes of this research show that the previous studies deployed many combinations of elements from the six-perspective mentioned above, leading to a wide range of fuel consumption and emissions savings. The study also concludes that the available fuel consumption and emissions models are relatively old. Hence, future research is needed to develop new fuel consumption and emissions models based on recently collected data.

The Impact of Unconditional Priority for Escorted Vehicles in Traffic Networks on Sustainable Urban Mobility

“…Many studies proved that traffic control and the better quality of the network have a direct impact on energy efficiency and the sustainability of traffic systems, especially in urban areas. According to the previous research carried out by the authors [9], where the overall benefit and the quality of traffic network management were influenced, the research in this paper includes the impact of unconditional priority on the emission of exhaust gases and fuel consumption in the city of Zagreb. Even though similar research was conducted regarding conditional priority relative to other vehicle categories (emergency vehicles, public transport vehicles, etc.…”

“…Also, it is possible to distinguish different causes of exhaust gas emissions. According to [9], nearly 22% of spent fuel is caused by excessive speeding, inefficient traffic control, ineffective and aggressive acceleration, and deceleration. As mentioned before, the C-ITS concept has the potential to enhance these parameters and address the underlying causes.…”

Estimation of Arrivals on Green at Signalized Intersections Using Stop-Bar Video Detection

“…Furthermore, a key “ingredient” for the accurate estimation of POG, Rp, and AT is the number of vehicles arriving on green, that is, arrivals on green (AOG). Numerous studies have used these measures to monitor progression performance quality ( 12 , 13 ) or even for signal timing optimization ( 14 – 16 ). Furthermore, traffic detection vendors around the United States have developed their hardware and software solutions to be capable of estimating these measures.…”