Optimizing Urban Bus Transit Network Design Can Lead to Greenhouse Gas Emissions Reduction

Abstract

The high contribution of greenhouse gas (GHG) emissions by the transportation sector calls for the development of emission reduction efforts. In this paper, we examine how efficient bus transit networks can contribute to these reduction measures. Utilizing continuum approximation methods and a case study in Barcelona, we show that efforts to decrease the costs of a transit system can lead to GHG emission reductions as well. We demonstrate GHG emission comparisons between an optimized bus network design in Barcelona and the existing system. The optimization of the system network design involves minimizing system costs and thereby determining optimal network layout and transit frequency. In this case study, not only does the cost-optimal design lead to a 17% reduction in total costs, but even more notably, the optimal design leads to a 50% reduction in GHG emissions. Furthermore, the level of service to the user is not detrimentally affected and, in fact, it is slightly improved. We, therefore, extrapolate and hypothesize that the optimization of transit networks in many cities would result in significant GHG emission reductions. The analysis in this paper specifically focuses on the effects of bus technology with fixed ridership corresponding to the Barcelona case study, but the methods implemented could be easily applied to other transit modes in different cities.

Emissions Trends and Drivers

“…Changes to the operation of public transportation systems (such as density of bus stops, distance from stops to households, duration and frequency of trip times, and lowering ridership costs) can result in a mode shift from private car trips to public transit trips (Cats et al 2017;Choi 2018;Carroll et al 2019). These changes in the public transit system operation and network optimisation have been shown to have reduced GHG emissions in cases such as San Francisco, where the cost optimisation of the transit network was estimated to decrease emissions by a factor of three (Cheng et al 2018) and Barcelona, where the optimisation of the urban bus system was estimated to reduce GHG emissions by 50% (Griswold et al 2017). For every 1% increase in investment in transit services and transit-oriented design, there is an estimated 0.16% reduction in private vehicle kilometres travelled per capita (McIntosh et al 2014).…”

Three Decades of Climate Mitigation Policy: What Has It Delivered?

“…The replacement of internal combustion engine vehicles by EVs holds a substantial mitigation potential, although empirical, ex post evidence is not yet substantive, given the early phase of the substitution process (see Section 3.5) (49,(189)(190)(191). Empirical literature on the emission reduction effect of policies that promote alternative modes of transport is scarce, but the available evidence suggests that investments in or the provision of public transport and cycling infrastructure reduces air pollution and congestion, and thereby GHG emissions (192)(193)(194)(195)(196)(197)(198)(199)(200)(201)(202)(203). Measures that have been empirically demonstrated to reduce demand and emissions from aviation include fuel and passenger taxes (204)(205)(206) and the construction of high-speed rail (207)(208)(209).…”

Joint optimization of bimodal transit networks in a heterogeneous environment considering vehicle emissions

“…Inspired by previous related studies (e.g., Sivakumaran et al, 2012;Griswold et al, 2013;Griswold et al, 2017;Luo and Kang, 2021), we consider a bimodal transit network with one CBD area (see Fig. 1).…”

“…Similar to previous studies (e.g., Sivakumaran et al, 2012;Griswold et al, 2013;Sivakumaran et al, 2014;Kim and Schonfeld, 2015;Griswold et al, 2017;Luo and Kang, 2021), a rectangular service area is designated with 𝐿𝐿= 20km and 𝑙𝑙 𝑖𝑖 (𝑥𝑥)=5km, ∀𝑥𝑥 ∈ [0, 𝐿𝐿].…”