Introducing a Novel Framework for the Analysis and Assessment of Transport Projects in City Regions
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1. Introduction
3. Methodology
3.1. Definition of Scope
The definition of scope is a critical part of the proposed framework as it affects the list of indicators to be calculated, the target values per indicator, and the delimitations of the assessment. It begins with formulating a vision of how the transport system should develop and how success will be measured in the entire city region. The following premise is underlying this study: “The Munich city region shall take significant action to transform its transport system in line with a sustainable development path. The transport system shall ensure accessibility for all citizens while achieving net zero carbon dioxide emissions and less primary energy consumption in accordance with current legislation”.
While selecting the indicators, the scope of the analysis and its delimitations need to be defined for the geographical area, the time horizon, the types of transport, and the transport relations. In this case, study, the following delimitations are used:
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Geographical area: Due to data availability, communicability, and functional adequacy (see Section 2.3), we use the MVV region in 2019 as a spatial delimitation.
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Intervention area: For testing the proposed methodology, one intervention area within the MVV region is defined as a sub-unit of the geographical area. This intervention area covers the geographical area of the U5 southeast extension and the area for accompanying push measures. It is shown in Figure 2.
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Years: The base year of the analysis is 2019. Indicator values are calculated for the years 2019 to 2055. A legal target for the climate neutrality of the transport system in Germany by 2045 has been established [35]. Allowing for some additional years of possible overshoot, we use the period until 2055 as the planning horizon for the MVV region. However, some compromises due to data availability are necessary. For instance, accessibility indicators are only modelled for the forecast year 2035. It was chosen for reasons of data availability. Additionally, this forecast year is currently used for official transport project assessments in the MVV region, ensuring comparability. For the years beyond 2035, travel demand projections were not available. Therefore, the transport demand impacts of the U5 southeast extension and accompanying push measures are assumed constant for the rest of the project’s life cycle.
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Types of transport: We only consider passenger transport in our study due to data availability and the fact that we assess a scheme with a public transport project that has a negligible impact on freight transport.
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Transport relations: Our study aims to analyse and assess the transport-related impacts within the MVV region. Hence, we only consider the transport relations starting and ending within the MVV region. The case study does not consider the through, inbound, and outbound traffic of the MVV region. In Germany, long-distance road, rail, and waterway networks are planned on a national scale in the process of the German Federal Transport Infrastructure Plan [36]. Consequently, if the methodology were applied at a broader geographic scale or even at the national level, then more transport relations would be included within the scope of assessment.
Next, we describe the indicators and their calculations in detail.
3.1.1. Accessibility to Jobs
with = accessibility per cell, = origin cell, = destination cell, = transport mode (car, public transit, bike), = workforce per cell (employed and self-employed), = travel impedance decay parameter (−0.0336 for MVV region), = modal share, and = travel impedance in minutes.
with A = compound accessibility index and p = population per cell.
3.1.2. Carbon Dioxide Emissions
with = carbon dioxide emissions in tons CO2 per year, = transport system (car, regional train, urban transit (S-Bahn), underground rail, tram, bus), = vehicle kilometres per year, and = carbon dioxide emission factor in gramme CO2 per vehicle kilometre.
Indirect emissions from fuel and electricity production are included in the emission factors. Upstream carbon dioxide emissions from infrastructure construction and vehicle manufacturing are omitted in this case study.
Emissions from freight transport are not calculated. Our scope of analysis is the regional transport relations within the MVV. Hence, emissions from through traffic, inbound, and outbound traffic are not computed.
3.1.3. Primary Energy Consumption
with = primary energy consumption in GJ per year, = transport system (car, regional train, urban transit (S-Bahn), underground rail, tram, bus), = vehicle kilometres per year, and = primary energy consumption factor in Joule per vehicle kilometre.
Energy consumption from freight transport is not calculated. Our scope of analysis is the regional transport relations within the MVV. Hence, energy consumption from through traffic, inbound traffic, and outbound traffic is not measured. By computing primary energy consumption, we also consider losses from energy conversion.
3.1.4. Costs
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Public transit operating costs;
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Infrastructure costs: project-specific investment costs, reinvestment, and residual values in 2055 according to standardised life cycles per infrastructure component;
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Maintenance cost: according to standardised maintenance cost rates per infrastructure component.
We use factor costs, i.e., net of tax. For ease of interpretation and comparability to the other assessment indicators, we calculate the NPV. All costs in the assessment period are discounted to the NPV in 2019 (at 2016 prices), using the same social discount rate of 1.7% as in the German national appraisal guideline. For reasons of comparability, we express costs in 2016 prices.
For reasons of data availability, we only measure the change in costs due to the transport scheme and do not estimate the sum of all investment, maintenance, and operating costs per year in the entire MVV region.
3.2. Cases
The traditional framework of transport appraisal distinguishes between a reference case and a project case. Then, the impacts of a specific project are calculated as differences in indicator values between the project case and the reference case.
In this paper, the reference case captures the forecast developments of the transport system in the MVV region. It includes all transport network changes expected to be effective by 2035 and additional public transit projects by 2045. It also incorporates a forecast of structural data, i.e., population and workforce per cell, and forecasted travel demand and travel time matrices. Lastly, the development of carbon dioxide emission factors and primary energy consumption factors per vehicle kilometre is projected based on assumptions of fleet change, efficiency gains, and changes in the mix of the electric power supply.
In contrast to traditional transport appraisal methods, this paper does not use a single project case to calculate the impacts of a scheme. Instead, the project case is split into two sequentially modelled cases. This procedure allows for separating the effects of the U5 southeast extension as a public transport infrastructure project and accompanying push measures that restrict car usage.
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Changes in the public transit network due to the U5 southeast extension in 2035 (in terms of additional underground stations, changes in the operating concept of underground services, changes in bus services);
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Resulting changes in the travel impedance matrices;
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Resulting changes in the travel demand matrices;
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Resulting changes in carbon dioxide emissions and primary energy consumption;
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Changes in investment, maintenance, and operating costs.
In this case study, we concentrate on designing a methodology that accomplishes the following:
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Shows where these push measures could be implemented from a regional accessibility perspective;
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Shows their effect on mobility behaviour, carbon dioxide emissions, and primary energy consumption in relation to the costs of the scheme. Other positive impacts of push measures on urban environments, quality of life, and quality of stay are neglected here, as well as possible negative impacts on the economic welfare of car users.
The travel time extensions for car usage in each transport cell in the intervention area are calculated as follows:
- 1.
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The effect of the U5 project on public transit accessibility in the intervention area is determined by calculating the change in public transit accessibility in the pull case compared to the reference case (rc). For this, the modal share in Formula (1) is neglected, and only accessibility for k = transit is calculated per cell:
× ∑ j w j e β r i j , t r a n s i t p u l l − ∑ j w j e β r i j , t r a n s i t r c - 2.
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can be expressed as a change of “weighted average public transit impedance in minutes per cell in the intervention area to reach jobs in the MVV region” by using a logarithmic transformation of accessibility per cell:
- 3.
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Next, this accessibility improvement in the public transit system is regarded as a potential to make car traffic per transport cell less attractive by implementing push measures. Hence, in the first term of Equation (7), car impedance surcharges per cell are set equal to the negative change in weighted average public transit impedance per cell in the intervention area. In the second term of Equation (7), this is scaled by the ratio of transit demand and car demand ( = travel demand per origin–destination relation in passengers per weekday) per cell:
∑ j d i j , c a r r c If a transport cell has a high ratio of transit to car demand, this indicates that sufficient services are available. It is, therefore, more accessible for car users to shift to public transit. Thus, these transport cells receive a higher car impedance surcharge in the push case. Instead, if the ratio of transit to car demand per transport cell is low, the car impedance surcharge is lower. Thereby, push measures are assigned to cells that both benefit from the pull project and allow travellers to shift to public transit.
- 4.
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In the final step, car impedance surcharges are converted into car travel time extensions in the push case, where is a conversion factor from the transport model:
This approach ensures that an adequate level of accessibility as part of a sustainable mobility strategy for the MVV region is maintained. In the case study, the accessibility target is defined as the level of the compound accessibility index in the reference case in 2035. Consequently, the compound accessibility index for the MVV region must remain constant before and after implementing the transport scheme. However, accessibility per cell, i.e., accessibility in different locations, can vary. This reflects the fact that by any intervention, it is nearly impossible to have only winners. There will almost always be winners and losers, be they people, transport users, or geographic areas. We argue that planning should provide an appropriate level of accessibility for the MVV region. Then, people and businesses can make their own location decisions.
with = travel demand per origin–destination relation in passengers per weekday, = origin cell, = destination cell, pull = pull case, push = push case, = elasticity of car travel demand with respect to car travel time changes, and = travel time in minutes. The car travel times in the push case () in Formula (9) include the car travel time extensions due to push measures at origin and/or destination. Next, an occupancy rate of 1.3 person-kilometres per vehicle kilometre and a demand scaling factor of 300 working days per year are applied to project the change in yearly vehicle kilometres. This procedure corresponds to the parameters specified in the German national appraisal guideline [37], which were calibrated for regional transport relations. Based on the change in car vehicle kilometres, the effects on passenger transport-related carbon dioxide emissions and primary energy consumption are calculated.
with = cross-elasticity of transit travel demand with respect to car travel time changes. The cross-elasticity is calculated per origin–destination relation according to Formula (11), using the elasticity of car demand, the ratio of car and transit demand per origin–destination relation, and the diversion factor () from car to transit. The diversion factor measures the proportion of car travellers diverting to or from car when the car travel time increases due to push measures.
In the proposed framework, the infrastructure project is bundled with accompanying push measures. The intervention area is based on the administrative and geographic boundaries where the measures are implemented, even though the impacts of the scheme also occur in other areas of the city region. We argue that the administrative geographic area is suitable for bundling projects into packages for the following reasons:
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Administrative responsibilities: Since all projects in a package are assessed jointly, the implementation of the entire package must be guaranteed. This is most likely if the projects fall under the responsibility of certain administrative authorities—municipalities or city districts—that can credibly guarantee implementation.
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Communication with citizens and various stakeholders: The acceptance of accompanying projects, e.g., street redesigns and parking reductions, is likely to increase if they are associated with improvements from a public transport infrastructure project. The idea of acceptance is also reflected in the concept of “push and pull measures” [34] or “carrots and sticks” [42].
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Strategic action and scaling for the city region: Geographically distinct intervention areas create the opportunity to develop a transport programme for the city region on a larger scale. Our proposed framework can assist this process by building on the analyses and assessment results to rank and prioritise schemes for many intervention areas.
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Clear attribution of impacts: There is a clear causal relationship between the transport project package and resulting changes in travel demand, carbon dioxide emissions, and primary energy consumption. It is irrelevant where the impacts occur. Therefore, we functionally attribute all indicator impacts to the project package of one intervention area, even if parts of the impacts occur outside the intervention area. For instance, imagine one person who lives inside the intervention area and whose workplace is outside the intervention area. Due to the scheme, this person might shift from using a car to taking public transit for their trip to work. Then, a part of the journey occurs within the intervention area and another part outside. In our framework, the reduction in car vehicle kilometres from the entire journey length would be functionally attributed to the transport scheme in the intervention area. This makes it possible to analyse and assess measures in several regional intervention areas and clearly attribute their effects without double-counting. Hence, stakeholders in a city region could develop project and policy packages for distinct intervention areas, and the methodology could assess the contribution of different intervention areas to region-wide targets for improving the plans and ranking them.
4. Findings
In the following sections, we report the target indicator values for our case study in the MVV region. Afterwards, the impacts of the project bundle, including the U5 southeast extension and accompanying push measures, on the selected indicators are analysed. Lastly, these impacts are assessed with a CEA.
4.1. Target Indicator Values
In this case study, we define the target gap as the difference between target indicator values and projected indicator values in the reference case. In the following sections, the contribution of the scheme to closing the target gap is assessed.
4.2. Impact Analysis
The effects of the car travel time extensions on mode choice and, thus, passenger transport-related carbon dioxide emissions and primary energy consumption are computed as described in the methodology section of this paper. Here, we only report the impact on the final indicators.
We find that the impacts of the U5 project are minimal compared with the reduction targets for carbon dioxide emissions and primary energy consumption from passenger transport within the MVV region. Considering changes in public transport services and modal shift away from cars, 18 kt CO2 are saved in the pull case compared to the reference case. The effect would be even smaller if carbon dioxide emissions from infrastructure construction were considered. If the push measures to restrict car usage are implemented, we expect an additional reduction of 9 kt CO2 in the period 2019 to 2055.
The indicator values reported here will be the basis for the assessment in the next section. Even if the accessibility indicator is not part of the strict effectiveness–cost assessment, we see a benefit in reporting the accessibility analysis as part of the overall methodology. These results can support the planning and decision-making process.
4.3. Assessment
We use three assessment indicators: First, an effectiveness-cost ratio describes the scheme’s effectiveness per million EUR of costs (NPV) in 2016 prices. Second, its inverse ratio can be interpreted as a cost-effectiveness indicator and can be compared with the costs of carbon dioxide abatement schemes or prices of emissions trading systems. Third, the scheme’s contribution to achieving the target indicator values is assessed. In our case study, this can be interpreted as a contribution to avoiding excess emissions, defined by the gap between target indicator values and projections in the reference case. This indicator is useful for assessing a transport programme for an entire region with schemes in multiple intervention areas, ensuring that the entire programme reaches a certain threshold, ideally 100% of the target indicator value.
The scheme in the intervention area is expected to achieve approximately 0.1% of the necessary reduction in carbon dioxide to achieve passenger transport emission targets in the entire MVV region. This effect is small considering the size of the intervention area: approximately five percent of the inhabitants of the MVV region will live in the intervention area in 2035. This indicates that the scheme would need to be about 50 times more effective to make a fair contribution to closing the target gap in the entire MVV region. Therefore, we conclude that the combined push and pull scheme’s impacts are low compared to the carbon dioxide emission target gap. Interpreting the assessment indicators with respect to primary energy consumption leads to similar conclusions.
No assessment is conducted for the compound accessibility index because it was used to derive the accompanying push measures, and it stays constant between the reference case and the push case.
We conclude that the contribution of the U5 southeast extension to passenger transport-related carbon dioxide emission targets and primary energy consumption targets in the MVV region is low, even when bundled with push measures that maintain the level of accessibility in the reference case. Not only is the effectiveness low, but cost effectiveness seems inferior to other policy options, considering that marginal CO2 abatement costs are more than 100 times as high as current certificate prices in the European Emissions Trading Scheme.
5. Discussion
Second, we see a benefit in selecting quantitative indicators because they reveal the magnitude of targets and the rate of goal achievement. This means, however, that the proposed methodology only works for indicators that can be measured on a metric scale. Additionally, this paper’s selected indicators neglect the distributional aspects of transport projects. In future applications, metric indicators of social and distributional aspects could be integrated, for instance, a dedicated accessibility index for vulnerable people or a Gini index of the spatial or personal accessibility distribution.
Third, concerning the assessment, while the proposed methodology permits a focus on individually chosen target indicators, there is a risk of arbitrarily selecting these indicators. In contrast to other methods, such as CBA with indicators grounded in welfare economics, the premise of this paper is to achieve quantitative targets with cost-effective means. Hence, CEA is used. Consequently, the assessment is incomplete since CEA reports effectiveness–cost ratios for each indicator without weighting and aggregating them into a final metric for decision support, such as a benefit–cost ratio. Reporting effectiveness–cost ratios per indicator can be regarded as a benefit in communicating results but also as a restriction, as it gives no definite decision advice, only decision guidance.
Fourth, applying the proposed methodology in our case study demonstrates that it can be operationalised for assessing concrete projects in distinct intervention areas of city regions. Nevertheless, there is a considerable status quo bias since the chosen target in this paper is to hold accessibility constant at the level of the reference case. This goal constitutes a sharp difference from the traditional approach in transport appraisal. The latter identifies the various impacts of a scheme and primarily assesses the benefits over the costs. Then, a scheme is beneficial if it improves on most assessment indicators. By contrast, in the case of this paper, the implicit question is how to best reduce emissions and energy consumption without decreasing accessibility. A path worth pursuing might be testing accessibility target indicators based on the urban structure of an area in future applications.
Fifth, we see an additional benefit of the approach presented in this paper for bundling transport pull and push measures. Independent of the assessment methodology, it might support various transport planning contexts, such as scaling street interventions and car-reduced neighbourhoods in a city region. Future applications could address the current restrictions of the selected accessibility index being incomplete, especially because it is not differentiated to specific transport user groups. Additionally, we must acknowledge that the approach of calculating travel time extensions for cars in selected transport cells is on a conceptual level and is still to be translated into concrete push measures for implementation. Lastly, future applications could consider relation-specific push measures to complement transport cell-specific push measures.
Sixth, the case study results suggest low carbon dioxide mitigation potentials by public transport infrastructure investment. Even when the U5 southeast extension is bundled with accessibility-neutral push measures, the contribution to passenger transport-related carbon dioxide emission targets and primary energy consumption targets in the city region is low. If carbon dioxide emissions and energy consumption during the building phase were also considered, the effectiveness–cost ratios would be even lower. The low CO2 effectiveness–cost ratio seems to be a matter of fact and not a restriction of the methodology. However, there are various other rationales for public transport infrastructure schemes, especially social and economic ones, and the methodological approach in this paper is prepared to integrate these in the form of quantitative indicators in future applications.
Seventh, we see the proposed methodology as a contribution to sustainable mobility planning, even though we must acknowledge that a theory about the determinants and the distributional aspects of welfare in the realm of transport does not back the proposed framework. Hence, it should be discussed based on something other than theory, e.g., concerning its potential to stimulate debate on alternative appraisal methods and foster integrated planning. Several promising alternative concepts and methods to traditional appraisal procedures have been operationalised in this paper. Therefore, we see this paper as a contribution regarding the following aspects:
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A new perspective complements mere forecasting approaches: Assuming all regulations and expected transport developments manifest in a projected reference case, the proposed methodology determines a city region’s residual scope of action to achieve its target indicator values.
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A new key analysis variable focuses on transport supply rather than transport demand: In this paper, the key indicator is an accessibility index. Hence, the approach becomes less demand-oriented and more focused on accessibility objectives.
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A new sequential calculation of three cases fosters integrated planning and assessment: The proposed methodology calculates a third case to bundle pull and push measures into a combined package for a specific intervention area of a city region. Additionally, the method breaks the vicious circle of infrastructure provision and induced traffic. As defined in the feedback model by Wegener [51], lower travel times and costs due to transport projects tend to increase the attractiveness of movement, thus changing location decisions, inducing movement, and, hence, new transport infrastructure construction. Mainstream transport appraisal typically neglects dynamic feedback loops due to transport and land use interactions by focusing on the user benefits of reduced travel times. This paper’s methodology can help avoid the transportation and land use feedback loop by holding accessibility constant, thereby counter-balancing accessibility improvements due to faster connections with push measures.
One way of shaping the transformation towards sustainable mobility can be described as “transition by design”. According to this understanding, the overarching goal is to create decision frameworks and guidance for long-term integrated urban and transport development to achieve sustainability targets. The methodology in this paper aligns with this goal. It could be adapted to include more sustainability indicators even though changing planning and funding processes is highly speculative, and assessing schemes for many distinct intervention areas of a region will take additional time and financial resources.
A different approach to “transition by design” is a concept we call “transition through rapid and effective action”. According to this understanding, there is no time left for changing planning and funding frameworks if legally binding carbon dioxide abatement targets are still to be achieved. As shown above, while the MVV region needs to be net climate-neutral by 2040, the infrastructure projects assessed are unlikely to even be built by then. In this agenda setting, the goal would be to identify the most cost-effective policies, ensuring that all selected policies will achieve the targets. The results in this paper suggest that the effectiveness of public transport infrastructure pull and push projects on carbon dioxide emissions is far from sufficient if accessibility must not decrease. Hence, “transition through rapid and effective action” would call for more effective schemes accepting accessibility reductions.
In either case, the methodology presented in this paper could guide decision-making processes. We regard it as a contribution towards strategic supply-side, accessibility-oriented urban transport planning and as a first step in a different direction towards a sustainable mobility planning paradigm.
6. Conclusions
This paper proposes and applies a novel approach for the ex ante assessment of transport projects in city regions. As an alternative to traditional building blocks of transport appraisal, the methodology combines an accessibility-focused perspective, a bundle of pull and push measures in a specific intervention area, quantitative target indicators as a complement to forecasting methods, and assessment based on effectiveness and costs.
Applying this approach to the case of the proposed U5 southeast extension and accompanying push measures in the Munich city region, we find a large gap between passenger transport-related carbon dioxide emission targets and projected emissions in a reference case. The same applies to passenger transport-related primary energy consumption. The contribution of the U5 southeast extension to closing these gaps is low, even when the project is bundled with push measures in the intervention area. Considering the substantial carbon dioxide emissions and primary energy consumption reduction targets, the findings indicate that large-scale public transport infrastructure projects perform poorly on an effectiveness–cost criterion if current accessibility levels are to be maintained.
Nevertheless, the proposed approach has several benefits. First, it has the potential to shift focus away from the individual impacts of large-scale transport infrastructure projects towards a process of integrated transport and spatial planning in a city region. Second, bundling pull and push measures fosters more comprehensive transport planning. Perhaps most importantly, it reveals the magnitude of transport-related targets and the interventions’ contribution to achieving them. Therefore, the proposed assessment framework can support strategic transport planning in city regions. Additionally, it can contribute to changing perspectives towards strategic accessibility-oriented urban transport planning and a sustainable mobility paradigm.
Future research could integrate further indicators, for instance, objectives of land use. This will reflect a more holistic set of sustainable development indicators by capturing the dimensions of transport (accessibility), environment (carbon dioxide, primary energy consumption), and space (spatial accessibility targets and transit-oriented development indicators).
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