Glen
Senior Member
http://www.iop.org/EJ/article/1748-9326/4/2/024008/erl9_2_024008.html
Discussion of the environmental performance of transit modes often focuses on the ranking of vehicles assuming average occupancy. This approach does not acknowledge that there are many conditions under which modes can perform equally. For example, an SUV (which is one of the worst energy performers) with 2 passengers (giving 3.5 MJ/PKT) is equivalent to a bus with 8 passengers. Similarly, CA HRT with 120 passengers (27% occupancy giving 1.8 MJ/PKT) is equivalent to a midsize aircraft with 105 passengers (75% occupancy). Similarly, commuter rail (with one of the highest average per-PKT NOX emission rates) at 34% occupancy (147 passengers) is equivalent to a bus with 13 passengers or a sedan with one passenger. Focusing on occupancy improvements does not acknowledge the sensitivity of performance to technological changes. For example, holding occupancy at the average, electric rail modes would have to decrease SO2 per-PKT emissions between 24 and 85% to compete with onroad modes, an effort that would have to focus on electricity fuel inputs and scrubbers at power plants.
Discussion of the environmental performance of transit modes often focuses on the ranking of vehicles assuming average occupancy. This approach does not acknowledge that there are many conditions under which modes can perform equally. For example, an SUV (which is one of the worst energy performers) with 2 passengers (giving 3.5 MJ/PKT) is equivalent to a bus with 8 passengers. Similarly, CA HRT with 120 passengers (27% occupancy giving 1.8 MJ/PKT) is equivalent to a midsize aircraft with 105 passengers (75% occupancy). Similarly, commuter rail (with one of the highest average per-PKT NOX emission rates) at 34% occupancy (147 passengers) is equivalent to a bus with 13 passengers or a sedan with one passenger. Focusing on occupancy improvements does not acknowledge the sensitivity of performance to technological changes. For example, holding occupancy at the average, electric rail modes would have to decrease SO2 per-PKT emissions between 24 and 85% to compete with onroad modes, an effort that would have to focus on electricity fuel inputs and scrubbers at power plants.