Unintended greenhouse gas consequences of lowering level of service in urban transit systems

Griswold, Julia B.; Cheng, Han; Madanat, Samer; Horvath, Arpad

doi:10.1088/1748-9326/9/12/124001

Cited by 9 publications

(9 citation statements)

References 13 publications

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“…Simulation modeling has been used as a way to understand the net influence on pollutant emissions made by the interplay between transit operations and personal vehicle traffic. Griswold et al (2014) used a simulation model of an abstract transit system to explore how transit level of service (LOS) impacts rider per-capita emissions. Their model showed that while during peak travel hours per-capita emissions were reduced by using transit, during off-peak hours transit actually increased per-capita emissions due to buses or trains.…”

Section: Simulation Modelingmentioning

confidence: 99%

Modeling net effects of transit operations on vehicle miles traveled, fuel consumption, carbon dioxide, and criteria air pollutant emissions in a mid-size US metro area: findings from Salt Lake City, UT

Mendoza

Büchert

Lin

2019

Environ. Res. Commun.

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The Utah Transit Authority (UTA) serves Utah's Wasatch Front, a rapidly growing conurbation with a current population of ∼1.8 M people. UTA uses an electronic fare collection (EFC) system that requires riders to tap on as they enter a bus or train and tap off as they exit, as well as an automated passenger counter (APC) system that counts interruptions of infrared beams across vehicle doorways as riders board and alight. We analyzed EFC and APC data for 2016, along with service schedules and routes from General Transit Feed Specification (GTFS) data, to estimate the impact of UTA on the air quality in its service region by accounting for vehicle miles traveled, gasoline gallons equivalent of fuel consumed, and multiple pollutant species emitted. Buses, light rail, and commuter rail were found to collectively offset approximately 1.5% of the onroad emissions from the counties served by UTA due to transit use replacing single passenger vehicle use. These offsets are not homogeneous; ridership drops significantly (∼20%-50% depending on the mode) during the summer months as some of the largest users are educational institutions with noticeable seasonal cycles. Low transit use during the weekend negates some of the air quality benefits as buses and trains travel at lower capacity. Central routes, particularly during peak travel hours provide noticeable congestion, fuel consumption, and pollutant emissions reduction due to trips taken by transit replacing personal vehicles but off-peak, and non-central routes, show lower benefits. Because the light rail is electric, its local air quality benefits are significant due to the electricity being produced primarily outside the airshed. Upgrading the bus fleet to 2010 model, and newer, diesel and compressed natural gas (CNG) buses, as well as modeling an envisioned change to Tier 3 locomotives for the commuter rail system, was found to significantly reduce regional nitrogen oxides (NO x ), fine particulate matter (PM 2.5 ), and sulfur oxides (SO x ) emissions.

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Section: Simulation Modelingmentioning

confidence: 99%

Modeling net effects of transit operations on vehicle miles traveled, fuel consumption, carbon dioxide, and criteria air pollutant emissions in a mid-size US metro area: findings from Salt Lake City, UT

Mendoza

Büchert

Lin

2019

Environ. Res. Commun.

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“…The formulation of the problem builds on the work of Sivakumaran et al (2014), Griswold et al (2013) and Griswold et al (2014). The mathematical formulation consists of optimizing the transit system design to achieve the lowest total costs and transit emissions possible.…”

Section: Formulationmentioning

confidence: 99%

“…In earlier work (Griswold et al, 2014), we explored the unintended consequences of such emission reduction efforts. We considered a hypothetical city with a grid trunk transit network, and compared four trunk line modes -bus, bus rapid transit (BRT), light rail transit (LRT), and metro -with walking as the access mode.…”

Section: Introductionmentioning

confidence: 99%

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Planning hierarchical urban transit systems for reductions in greenhouse gas emissions

Cheng

Madanat

Horvath

2016

Transportation Research Part D: Transport and Environment

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Public transit systems with high occupancy can save greenhouse gas (GHG) emissions. However, current transit systems had not been designed to reduce environmental impacts. This motivates the study of the benefits of optimal design and operational approaches to reducing the environmental impacts of transit systems. Transit agencies could resort to level-of-service (LOS) changes, for example, reductions in vehicle kilometers traveled. In previous work, we explored the unintended consequences of lowering transit LOS on emissions from a single-technology transit systems. Herein we extend the analysis to account for a more realistic case: a transit system with hierarchical structure (trunk and the feeder lines) providing service subject to demand elasticity. By considering the interactions between the trunk and the feeder systems, we provide a quantitative basis for designing and operating integrated urban transit systems that can reduce GHG emissions and societal costs. We find that large cities may achieve societal cost as well as emission savings by employing a hierarchical structure, while the non-hierarchical structure may be better for small cities. Highly elastic transit demand may cancel emission reduction potentials, yet for mass transit modes these potentials are still significant. Transit networks with buses, bus rapid transit or light rail as trunk transit modes should be designed and operated near the cost-optimal point when the demand is highly elastic, while this is not required for metro.

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“…Within transportation, the idea has been applied to public transportation systems (Griswold et al 2013(Griswold et al , 2014. Outside of transportation, researchers have examined tradeoffs with other technologies, such as water distribution systems (Wu et al 2009) and cogeneration (Bamufleh et al 2013).…”

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confidence: 99%

The effect of agency budgets on minimizing greenhouse gas emissions from road rehabilitation policies

Reger

Madanat²,

Horvath

2015

Environ. Res. Lett.

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Transportation agencies are being urged to reduce their greenhouse gas (GHG) emissions. One possible solution within their scope is to alter their pavement management system to include environmental impacts. Managing pavement assets is important because poor road conditions lead to increased fuel consumption of vehicles. Rehabilitation activities improve pavement condition, but require materials and construction equipment, which produce GHG emissions as well. The agency's role is to decide when to rehabilitate the road segments in the network. In previous work, we sought to minimize total societal costs (user and agency costs combined) subject to an emissions constraint for a road network, and demonstrated that there exists a range of potentially optimal solutions (a Pareto frontier) with tradeoffs between costs and GHG emissions. However, we did not account for the case where the available financial budget to the agency is binding. This letter considers an agency whose main goal is to reduce its carbon footprint while operating under a constrained financial budget. A Lagrangian dual solution methodology is applied, which selects the optimal timing and optimal action from a set of alternatives for each segment. This formulation quantifies GHG emission savings per additional dollar of agency budget spent, which can be used in a cap-and-trade system or to make budget decisions. We discuss the importance of communication between agencies and their legislature that sets the financial budgets to implement sustainable policies. We show that for a case study of Californian roads, it is optimal to apply frequent, thin overlays as opposed to the less frequent, thick overlays recommended in the literature if the objective is to minimize GHG emissions. A promising new technology, warm-mix asphalt, will have a negligible effect on reducing GHG emissions for road resurfacing under constrained budgets.

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Unintended greenhouse gas consequences of lowering level of service in urban transit systems

Cited by 9 publications

References 13 publications

Modeling net effects of transit operations on vehicle miles traveled, fuel consumption, carbon dioxide, and criteria air pollutant emissions in a mid-size US metro area: findings from Salt Lake City, UT

Modeling net effects of transit operations on vehicle miles traveled, fuel consumption, carbon dioxide, and criteria air pollutant emissions in a mid-size US metro area: findings from Salt Lake City, UT

Planning hierarchical urban transit systems for reductions in greenhouse gas emissions

The effect of agency budgets on minimizing greenhouse gas emissions from road rehabilitation policies

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