Selection of Intersection Groups for Congestion Mitigation and Energy Conservation in Urban Road Engineering

Traffic congestion not only severely impacts the quality of residents' daily travel and increases travel costs, but also triggers traffic accidents, causes environmental pollution, and leads to resource wastage. There is a practical need for implementing engineering measures simultaneously at multiple intersections during urban road traffic congestion mitigation, necessitating in-depth research on the selection of critical intersection clusters. Based on existing research, the relationship between vehicle emissions and saturation degree was derived. The network efficiency evaluation metric was refined using saturation degree, and a model linking vehicle emissions to network efficiency was established. A validation experiment was designed using the core road network of Xining City, Qinghai Province as an example. Results indicate that vehicular exhaust emissions per kilometer are proportional to the saturation degree metric value. The network efficiency metric value is inversely proportional to the overall (or average) saturation degree of the network. Vehicular exhaust emissions exhibit an inverse relationship with network efficiency. As the road traffic operational state shifts from congestion to smooth flow, for every 1-unit increase in network efficiency value, the average exhaust emissions per vehicle per kilometer decrease by 3.976 kg. Different congestion mitigation node selection schemes correspond to varying total emission reductions during the morning peak. If ranked by the magnitude of change in network efficiency (from largest increase to smallest), the corresponding total morning peak emission reductions gradually decrease in a stepwise manner. According to the 2 out of 60 and 3 out of 60 experimental results, compared to the worst node cluster selection scheme, the optimal node cluster selection scheme can reduce vehicular exhaust emissions by 4441 kg and 6616 kg, respectively.