Urban rail is largely electrified in which case its tail-pipe emissions are zero. Climate externalities from electric rail are zero according to the European Handbook on the external costs of transport (though the same is not true for Diesel powered trains).

By fostering higher density development, rail indirectly contributes towards urban forms that favour more Public Transport and non-motorized modes and greater overall efficiency. For instance, public transport-oriented compact cities, combined with improved infrastructure for non-motorised transport, could reduce GHG intensities by 20 to 50 per cent compared to 2010 levels. Controlling for other factors, the difference in transport intensity between high- and low-density areas can be more than 40% in vehicle-kilometres-travelled per capita.

But there are two important factors influencing rail's ability to reduce the carbon intensity of transport: Enough demand (high average loads) and the electricity mix that powers the trains. A new metro line that leads to high construction emissions (significant elevated or underground construction), has low frequencies and average loads and is powered by an electricity mix with high carbon emissions will not lead to GHG savings.

The CO2 mitigation impact in this case depends on the chosen technology, as well as on the energy grid of the context at hand. Hydrogen fuel cells are estimated to have mitigation potential: in the UK, simulations for a specific route showed that a hydrogen powered train and hydrogen-hybrid train led to 59% and 77% CO2 decrease compared to diesel propulsion. An overall analysis in Europe set the potential for CO2 mitigation at around 40%, compared to a diesel-propelled train scenario. Hydrogen potential depends on how it was generated: in the USA a recent analysis showed that hydrogen energy generated with renewable sources brings about 20 times more benefits than thermal electricity or natural gas generated hydrogen. Battery mitigation potential has been set lower: the same analysis in the USA estimates that the benefits brought about by batteries in terms of decarbonisation potential stand midway between hydrogen-based and diesel technologies.

In Montreal, a full electrification of a railway line brought about 98% of CO2 mitigation, compared to only a maximum of around 70% for renewable energy-generated hydrogen - most of the electricity produced in Montreal comes from hydroelectric plants.

Electrification will generate net new energy demand for the utility companies. There will need to be adequate incremental capacity available to sustain train operations. The rail operators no longer provide their own power (as in the past) and will rely on the adequacy of national or international pooled grid supplies for effective operation. Given the rail system represents a wholly new market for the power suppliers potential collaboration between the generators, rail infrastructure managers and train operators might be useful developmental and commercial model to develop.

On average, trains are eight times more energy efficient than trucks per tonne of freight carried. Emissions intensity of freight rail is nearly ten-times lower than that of trucks (in tkm). Electric traction has zero emissions at the point of use and can be carbon neutral using hydro, solar and wind inputs. Electrified traction effectively breaks the dependency of transport on liquid hydrocarbon inputs. The exact CO2 benefits of rail freight compared to road depend on a host of issues: average loads, energy source for the train (electric or diesel), energy mix of the electric grid, size of the train or need of last/first-mile road component.

Electric trains in Europe or heavy large trains in the US compare much better with trucks than a smaller diesel powered train not fully loaded. Rail movements siding-to-siding not requiring a road component (e.g. between a Port and large industry or mine, or between industries) or where the road component is minimized (e.g. between a Port and an inland dry port) compare more favourably than when extensive road transport is required at the end/start of the rail component.

From Basel, Switzerland to the Port of Rotterdam, Netherlands CO2 emissions from rail are 8 times less than by road, but on other routes this gap can be lower.

Home deliveries in urban areas tend to generate more traffic than pick-up points because they are, by design, less efficient.

Pick-up points reduce vehicle kilometres travelled by eliminating failed delivery attempts and by improving the efficiency of deliveries since there are less destinations for shipments. The reduced congestion resulting from use of pick-up points translates to lower levels of pollution and CO2 emissions from freight vehicles as well as other vehicles that are inadvertently affected.

A case study in Italy comparing home deliveries to pick-up point deliveries estimated the latter method to reduce CO2 emissions by 21%.

A comparison of 56 cities within 32 countries across the globe estimated that pick-up points can reduce congestion by 36% and emissions by 4%.

A study on InPost lockers showed that pick-up points allowed for 600 packages to be delivered during 24 hours, with trucks traveling 70 km total, whereas home delivery would only allow for 60 packages to be delivered and would require 150 km of vehicle movement for the same period of time. The CO2 consumption for the given example would be 1,516 tons for InPost lockers versus 32,500 tons for traditional deliveries, which means pick-up points generated more than 21 times less emissions.

A study on cities in France estimated that replacing freight shipments using diesel vehicles with electric vehicles (with 6 ton payload) would reduce CO2 emissions by 60% in urban areas of over 100 000 inhabitants. 

Using electric LDV instead of fossil-fuelled LDV for parcel deliveries in Rio de Janeiro, Brazil, was estimated to reduce CO2 emissions by 25%.

A study on deliveries from a suburban London depot to London showed a 54% reduction in CO2 emissions per parcel when diesel vehicles were replaced by a micro-consolidation centre and electric vehicles and tricycles. 

The CO2 impacts are linked to the characteristics of the fuel production pathway, the carbon content of the fuel and the origin of the carbon.

Increasing the availability of charging and refuelling stations can increase adoption of cleaner vehicle technologies. This is linked to CO2 emissions reductions for both types of infrastructures. The implementation of 50 thousand fast charging stations in the US can be linked to a projected 7.4% decrease in emissions by 2050 compared to the baseline.

The CO2 mitigation potential will depend on various factors. First, it will depend on the density of previously existing infrastructure. At the European Union level, by 2020 electric charging infrastructure in northern countries will be beyond 2025 targets. This would decrease effectiveness of measures for decreasing emissions.  it will also depend on the attractiveness of the charging infrastructure for the user. For the previously mentioned US study, the impact of putting 50 000 fast-charging stations nation-wide is seen to be wider than making available 500 000 slow charging stations. The mitigation potential will also depend on where the charging is done and at which period. Work-place charging is seen as a particularly attractive option in the US, where it is associated with as much as 20 times more purchase of electric vehicles than non-workplace charging. Impact on CO2 emissions will ultimately depend on the energy mix of the grid, and the main type of energy fuelling the infrastructure at the moment of charging.

GHG emission reductions resulting from the mandatory blending of low-carbon fuels result from the differences in well-to-wheel emissions characterizing different fuels in the final blend and the relative weight (in term s of volume or energy content) that each of the different fuels has in it. GHG emission savings are therefore primarily imputable to fuel/energy vector switching occurring without changes in powertrain technologies, displacing GHG emissions from fossil fuels thanks to the adoption of fuels/energy vectors produced from renewable carbon streams, such biogas and advanced biofuels, taking into account of GHG emissions occurring during fuel/energy vector production and use.

As in the case of low-carbon fuel standards, the regulatory nature of blending mandates places greater certitude on the achievement of GHG emission reductions than on the implicit cost of achieving them.             

GHG emission reductions in an LCFS are achieved through three main compliance categories:

i) Improved energy efficiency, renewable energy integration and carbon capture, use and storage for production of the fuel/energy vector.

ii) Fuel/energy vector switching occurring without changes in powertrain technologies, displacing GHG emissions from fossil fuels thanks to the adoption of fuels/energy vectors produced from renewable carbon streams, such biogas, advanced biofuels and PIX fuels, taking into account of GHG emissions occurring during fuel/energy vector production and use.

iii) Fuel/energy vector switching occurring thanks to changes in powertrain technologies such as battery electric and hydrogen fuel cell vehicles, taking account of changes in GHG emissions due to higher energy conversion efficiency in the powertrain, differences in the carbon intensity of the production of the energy vector and, ideally, also taking into account the differences in GHG emissions due to the manufacturing of vehicles using different powertrains. 

A key feature of a LCFS is that by design, it places greater certainty on the achievement of GHG emission reductions than on the implicit cost of achieving them. A LCFS can be designed to include cost-containment mechanism providing an additional route to compliance by capping to the cost of the credits. This reduces the certainty on the achievement of emission reductions, limits the maximum subsidy that the LCFS can give to credit generators and ensures that the overall impact on fuel prices of the policy instrument is subject to an upper threshold.

Asset sharing for the pooling of freight resources has been linked to CO2 mitigation benefits. In one UK study, reductions of up to 40% were observed.

EU CO3 project generated case study estimates of CO2 savings from horizontal collaboration above 15%. Also, UK Starfish projects modelling impact of multi-lateral collaboration on CO2 emissions of around 14%. In Bogota, a collaborative network of shared delivery routes and depot infrastructure is seen to be linked to a reduction of travel distances and related CO2 emissions of more than 25% compared to a non-collaborative scenario.

Intermodal rail is of primary importance to support long-distance trade corridors and inland ports in North America. It accounts for close to 40% of all the ton-miles transported in the United States, while in Europe this share is around 9%.

Following a rail oriented strategy to develop their hinterland the Port of Barcelona increased by a factor of 6 the TEUs (Twenty-foot Equivalent Unit) moved by rail from/to the port, the improvement of port side terminals and inland dry ports in Iberia were decisive for these results.

Improvements of operations at terminals can also decrease emissions from handling cargo at the interfaces. These reductions can go up to 50% of CO2 emissions.

From Basel, Switzerland to the Port of Rotterdam, Netherlands CO2 emissions from rail are eight times less than by road (though this gap can change depending on several factors, e.g. train propulsion, electricity mix, train size and average load). Improved intermodal transfer is one of several factors promoting a modal shift to lower carbon modes. For more numbers on CO2 emissions decrease from multimodal and rail solutions check the Enhanced & expanded Rail for freight measure.