The Connecticut Academy of Science and Engineering, on behalf of the Connecticut Department of Transportation (CTDOT), studied strategies to minimize the carbon footprint of CTDOT's bus operations. The investigation included literature review, operations analysis, and conducting interviews with transportation officials to understand overall benefits and savings of identified transition strategies. The analysis included bus operations, facilities, and equipment, though it did not address the emissions associated with supply chain operations.
CTDOT operates a total of 549 buses, with greenhouse gas emissions total estimated to be 0.07 million metric tons of Carbon dioxide equivalent (MMTCO2e), with 0.05 MMTCO2e of that total coming from fleet emissions.
The researchers developed the following recommendations, which are grouped by the area of operations they apply to:
Rolling Stock: As previously discussed, it was found that the majority of emissions arising from CTtransit operations originated from the bus fleet.
- A transition away from diesel buses would bring the most significant health benefits and cost reductions of any specific change, in addition to improving the social cost of carbon benefits associated with greenhouse gas (GHG) reduction.
Facilities: There were a number of suggestions for how CTtransit should manage its facilities, although, as a group, facility operations produced the least significant proportion of the agency's emissions.
- Hold to high performance buildings guidelines, such as LEED or Green Globes USA design specifications, whenever possible in the construction of public transit facilities.
- Research the potential of deploying behind-the-meter installations of renewable energy, and include both it and virtual net metering as part of facilities planning and maintenance. Virtual net metering allows surplus generator production to be reassigned to other metered accounts.
- Explore the assorted recommendations of the 2014 CASE study conducted for CTDOT, such as holding an energy audit, transitioning to LED lighting, and utilizing radiant floor heating.
Resilience: There are potential negative consequence of converting to an entirely battery electric bus fleet; in the even to of power outage, it may be difficult or impossible to maintain basic operations. Some suggestions to mitigate this included the following:
- Determination of minimum operations that would need to be maintained in a variety of emergency scenarios. This may include maintaining a certain minimum proportion of diesel or hybrid diesel vehicles.
- Leveraging existing resources, such as the state's reserve diesel fuel, to power hybrid buses or generators for electric buses.
- Explore possible benefits of battery electric buses in emergency situations, such as being able to use the buses to power critical response infrastructure during power outages.
- The study's authors strongly recommend periodically revisiting its conclusions on a periodic basis to update assumptions or perform additional analysis.
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