Reviewers’ Comments

Authors’ Response

Reviewer 1

the manuscript has some grammatical errors and typos . The manuscript does not comply with the journal template in several parts. write all acronyms in extended form when they are first included in the text

The revised manuscript has been carefully checked are errors are identified with the tracked changes in red (attached below

MDPI will format the final manuscript

Acronyms are spelt out

The novelty of the research should be better emphasised in the introductory part

The introduction has been completely rewritten to cover this criticism

include more details regarding the choice of case study 

Details of the case study are now included in the introduction as follows:

Under the Australian Constitution of 1901, the States and Territories have the major responsibilities for infrastructure (energy systems, transport systems and urban developments) with the national government being responsible for defence and foreign affairs and finance and taxation (grants are distributed to the states and territories). The Constitution also established a new capital city on 2348 km² of land appropriated from New South Wales (designated at the Australian Capital Territory). The layout of Canberra, as a planned garden city (418 km²), was based on an international competition won by Walter Burley Griffin in 1912 [8], and this became the Gazetted Plan of 1925 [9]. However, for a variety of political and economic reasons, Canberra developed rapidly only in the post-Second World War era at a time when private vehicle ownership in Australia was exploding. When the National Capital Development Corporation commenced its land-use and transport planning activities in 1958, the population was 39,000, and the number of vehicles had trebled from 1950. The urban structure in the long-term plan was a series of free-standing towns arranged in a Y shape with open space surrounding each town. At the heart of this layout is Griffin’s architectural design with a parliamentary area and a civic centre. A public transport spine connects the town and civic centres, and an extensive peripheral freeway system negates the intrusion of through traffic into the urban fabric [10].

Canberra represents a good example of a low density, car-dependent city developed during the motor-way age where a major policy challenge is to eliminate vehicle emissions from its transport sector. The city covers 418 square kilometres and has an urban density (in 2016) of nearly 5 persons per hectare. At the 2021 Census of Population and Housing 53 per cent of households owned two or more cars, and only 5.5 per cent of households did not own a car (https://profile.id.com.au/australia/car-ownership?WebID=250). The ACT Government recognises that one of the greatest sustainability challenges is the transport sector because it contributes 60 per cent of all emissions under its jurisdiction [11, p. 1]. The estimated resident population for 2024 is 477,567 (available at: https://worldpopulationreview.com/world-cities/canberra-population). According to data in [11], passenger vehicles annually travel some 3,900 million kilometres and are responsible for 82 percent of this travel demand. Journey-to -work travel is dominated by the car (80 per cent). Bus and tram usage is 8 percent, and active transport is made up of cycling 5 per cent and walking 3 per cent. Between October 2020 and March 2021, the mean daily number of e-scooter trips in the trial area of inner Canberra was 4, 479 [12, p.14] – 0.6 per cent of all daily trips.

In its planning strategy to minimise greenhouse gas emissions, the ACT Government is committed to consolidating Canberra's position as “a world-leading sustainable city” [13]. The ACT Government was the first state or territory in Australia to appoint a Sustainability Commissioner, and its State of the Environment reporting provides data to analyse trends in emissions and policies for their mitigation. There is strong community support for this sustainability goal. A sample of residents questioned about quality of life in Canberra in 2012 found that sustainability and the environment were key factors [14]. More specifically, a recent national survey found that two-thirds of Canberra’s citizens nominated climate change as the number one threat to humanity [15]. Data from the Australian Capital Territory (ACT) allows us to describe, and quantitatively analyse, the long-term effectiveness of land-use, transport, and environmental policies.

Insert more commentary to accompany figure 2

The peak monthly ridership of 450,000 was recorded in May 2019 - soon after the light rail commenced services. As happened throughout the world, there was significant drop in ridership during covid-19 lockdowns in 2020 and 2021. Although patronage has steading increased from September 2021 until May 2024, it has not yet climbed to its peak level in May 2019. This is possibly a reflection of more people working from home either for part of the week or working from home full time.

rewrite better in the conclusions to which actors the results of this research could be useful

This important point has been covered in the Discussion that has been entirely rewritten

Reviewer 2

Authors’ Response

I only miss to point out the threats of e-vehicles due to the production processes of the batteries and the after-use of them. Could you please reflect to this issue?

Thank you for pointing out this important omission. We have added:

The manufacture of vehicles and EV batteries are energy-intensive processes that emit greenhouse gases that are not considered in this paper. Once an EV battery is no longer suitable for use in vehicles, it can be repurposed for other applications. EV batteries require careful disposal: if left in landfills they can leak into the soil and ground water; if recycled materials can be reused to manufacture new batteries [ref number]. The rates of recycling EV batteries have been low because current recycling process are complicated and costly, requiring specialised facilities and skilled labour.  Without strong economic incentives or regulations by governments to support recycling, the industry finds it hard to improve sustainable battery disposal and reuse.

Christie, C. (2024) The truth about EV battery recycling. HERE Technologies, 31 May, 2024. Available at https://www.here.com/learn/blog/electric-vehicle-battery-recycling (accessed 16 July 2024)

c

1. References are needed for the first sentence of section 3.2.

2. There two tables named Table 2.

3. The cost of electrical cars

the recycling of the batteries needs to be further discussed.

These have been added

Corrected

Average costs in Australia have been inserted into the text where appropriate

Thank you for pointing out this important omission. We have added:

The manufacture of vehicles and EV batteries are energy-intensive processes that emit greenhouse gases that are not considered in this paper. Once an EV battery is no longer suitable for use in vehicles, it can be repurposed for other applications. EV batteries require careful disposal: if left in landfills they can leak into the soil and groundwater; if recycled materials can be reused to manufacture new batteries [ref number]. The rates of recycling EV batteries have been low because current recycling process are complicated and costly, requiring specialised facilities and skilled labour.  Without strong economic incentives or regulations by governments to support recycling, the industry finds it hard to improve sustainable battery disposal and reuse.

Reviewer’s Comments

Authors’ Response

(1) The methodology section could be expanded to provide more details on the data collection and analysis processes. While the authors mention using various government documents and reports, a more systematic explanation of how these were selected and analyzed would strengthen the paper's credibility.

Thank you for this important point. We have addressed this in the revised methodology.

As our informants have been senior public servants that span the decades from the establishment of the National Development Commission in 1957 to the present day, and have asked them to identify any key documents that we had not reviewe Therefore. we are confident that the data base for our analysis is comprehensive.

The selection process of these documents are also described in the Introduction section as we think it fits well in the section.

(2) The analysis of policy effectiveness is thorough, but could benefit from a more structured presentation. Consider organizing the findings into clear subsections based on different policy areas (e.g., land-use planning, public transport investment, cycling infrastructure, electric vehicle adoption) to improve readability.

The Discussion section has been completely rewritten (see manuscript revision with tracked changes below) and is organised along ther lines that the reviewer has suggested.

(3) The paper would be strengthened by including more comparative analysis with other low-density cities facing similar challenges.

This could help readers understand how the ACT's experiences and policy outcomes relate to broader trends in sustainable urban transport.

Based on another reviewer’s comment we have changed the title and reduced any emphasis in our manuscript on low density cities.

The reviewer does make an important point in putting the ACT experience in a global city comparison. In the discussion section we have made reference to the data base, C40 – a network of mayors representing leading cities of the world who are committed to policies that counter climate change (Available at: https://www.c40.org/research/accessed 3 August 2024)

(4) While the paper touches on future developments like autonomous vehicles, a more in-depth discussion of the long-term implications of current policies and emerging technologies would enhance its value for policymakers and urban planners.

Post submission of this manuscript, one of the authors has published a paper on AVs and the built form so a brief summary has been made for inclusion in the revision Discussion):

Some potential weaknesses and areas for improvement include:

(1)    The paper could benefit from a more explicit theoretical framework to guide the analysis of policy effectiveness.

(2)    The paper could conduct an in-depth analysis of the specific measures and execution of policies, such as the detailed criteria for financial incentives, the construction planning of charging facilities, and the specific measures of traffic management, to more accurately assess the effectiveness of the policies.

The paper could explore more deeply the social equity implications of various transport policies, particularly in the context of a low-density city.

Objectively assess the potential risks and challenges of autonomous vehicles and propose corresponding countermeasures.

Revised Discussion first paragraph especially framework developed by German Government

Under an agreement amongst all Australian states, territories and local government every program and policy must be assessed from the perspective of its potential economic, social and environmental impacts. A business case must be prepared (in essence, a summary of an environmental impact statement) for decision makers that explains the costs and benefits with quantitative and qualitative data. An example of this reporting is contained in Canberra Light Rail Stage 2A: Economic Analysis [122].

Added under autonomous vehicles and see above response.

There is an emerging literature on the potential impacts of fully autonomous vehicles in the city [123 – 125]. Westerman and Black have published a detailed paper on preparing for the transition of autonomous vehicles in urban areas, including a case study of a typical Canberra suburb [19, Fig,9]. Fully autonomous vehicles will be powered by renewable energy sources, either by electric batteries or hydrogen fuel cells, thereby eliminating harmful tailpipe emissions. Mobility hubs serviced by fully autonomous taxi services provide on-demand, twenty-four hour services for all, thereby allowing equity in access to mobility, shifting demand towards road-based and rail public transport. Also, mobility hubs have implications for reducing private vehicle ownership and for lowering space requirements for parking. There are further opportunities to develop mobility hubs as transit-oriented developments with basement rail systems and aerial services on the roof. As AVs will operate in precincts there are opportunities for community engagement and management in the future.

The key point is that fully autonomous vehicles, combined with mobility hubs, can enhance travel patterns for everyone, and in a sustainable way. This level of mobility cannot be achieved without mobility hubs. AVs should not use streets to roam and clutter them. Mobility hubs enable maintenance and charging and connect AV taxis with public transport. Movement corridors link precincts: therefore, risk management plans must be formulated to reduce vehicular traffic and pedestrian accidents.

Some figures and tables could be improved for clarity, particularly Figure 1 which appears to be low resolution.

Whilst Figure 1 contains place names in very small font the purpose of this figure is to illustrate the areas served by e-scooters and recent extensions shown in the coloured areas and we believe it is fit for purpose. The tables are formatted to the requirements of the journal (authors prefer the inclusion of delineating lines).

Reviewer 5

Authors’ Responses

The assertion that "the transport sector contributes 60 per cent of all emissions under [the Australian Capital Territory's] jurisdiction" lacks substantiation. Please provide adequate justification for this claim based on reliable data sources.

because it contributes 60 per cent of all emissions under its jurisdiction

reference added  [6, p. 1]. 6. ACT Government . Sustainable transport and travel in the ACT, 2024. Available at: . https://www.climatechoices.act.gov.au/transport-and-travel, (accessed 13 July 2024).

The emphasis on "Net-Zero Emissions" throughout the paper requires clarification on its relevance to the concept of low carbon.

How do these concepts interrelate within the paper's thematic framework?

Thank you for this point that we have clarified as follows:

The International Energy Agency's “Net Zero Scenario”[1] aims to “decarbonise transport by implementing a broad set of policies to encourage shifts to the least carbon-intensive travel options and operational and technical energy efficiency measures to reduce the carbon intensity of all transport modes”. In the case of urban transport, this includes the use of biofuels, and the substitution of fully electric or hydrogen fuel cell vehicles for petrol and diesel vehicles in passenger and commercial transport, and a modal switch from personal to public transport (with buses powered by electricity or hydrogen fuel cells). Whilst the decarbonisation of the economy represents national responses that counter climate change and global warming (for European countries, see, for example, [2]). At the city scale there are a wider set of economic, social and environmental issues that require policies to achieve more sustainable development, including the reduction in harmful vehicle emissions from the transport sector.

Using a series of indicators relevant to sustainable development goals (SDG), the World Health Organization [3] calls for a reduction in deaths and diseases from air pollution (SDG 3.9.1) and an improvement in cities of their air quality (SDG 11.6.2) .A major source of particulate matter and greenhouse gas emissions are from urban activities of which transport is a major contributor [4]. The global public health impacts of poor ambient air quality include lung cancer attributed to diesel engine fine particular matter [5], heart disease and stroke from fine particulate matter and from concentrations of ground level ozone [6].

One mainstream policy by national governments to improve urban air quality is based on the technology of vehicle engine design and manufacture by setting emission targets [7], that also aligns with decarbonisation of the transport sector, but there is also a raft of land-use, transport and the environment policies that are purported to contribute to reducing emissions in the urban transport sector.

Decarbonised economy has been addressed in the introduction and two references added in Table 1 (these policies align closely with our reference to policies on net-zero emissions)

Inviting senior ACT public servants for feedback on the draft is noted in the Acknowledgement section, which should be clarified as a review process rather than a methodological approach. Details regarding their specific contributions, evaluation criteria, and whether this constitutes formal research feedback should be explicitly stated or categorized appropriately.

This is clarified under methodology

The research scope does not align with the title's emphasis on "Low-Density Cities." The absence of relevant references (e.g., from 19 to 42) that directly address or contextualize this keyword further underscores a lack of thematic coherence, resulting in a tangential discussion.

Thank you for pointing this out. Low Density Cities has been removed from the title and we have also eliminated such references in the text unless it is necessary when mentioning Canberra

Clarify the term "YEAR" referenced in Table 2 for better comprehension. The presence of two Table 2 instances requires rectification for clarity and consistency.

Dates clarified and table numbering has been corrected

Sections 4.1 to 4.5 inadequately define their objectives, particularly concerning "zero-emission" goals.

Additionally, the structural organization within these sections is unclear, leaving ambiguity regarding whether they aim to discuss current status or identify existing issues.

We believe the revisions and the entirely new Discussion section address this.

Define the criteria used to classify a policy as "zero-emission," such as the "Long-term strategic land use/transport plan (Y-Plan)" mentioned in Table 3.

This policy aimed at distributing land use in free-standing new towns (districts) surrounded by a generous amount of natural  landscape to achieve an equitable urban form, and a uncongested highway system linking each town. The aim was to reduce distances travelled (emissions are proportional to distance travelled). The behavioural response of commuters has been towards maximization of distance travelled thereby providing an example of a policy failure. This example also suggests that policies of higher density that appear to contain trip lengths will do little to reduce vehicle emissions

Assess whether the policies listed in Table 3 are pertinent to low-density contexts, aligning with the paper's focus.

This has been addressed in the new section 5

Table 2's title, "The Spatial Distribution of Employment in Town Centres – The Y-Plan at Half-a-Million Population, and the 2001 and 2017 Census Figures," appears off-topic and requires clarification or adjustment to better align with the paper's objectives.

This is clarified in section 5 based on a fundamental relationship between travel distance, fuel consumption and vehicle emissions (subject to the driving cycle imposed by road traffic congestion)

Please elaborate further on the specific contributions of this paper to the existing body of literature.

It is a list of policies without enough discussion on the Effectiveness of Policies in Low-Density Cities.

The introduction has been re-written to include this

The discussion section now addresses this not the emphasis on low-densit cities has been reduced throughout the revised manuscript (see below in tracked changes)

Referee’s Comments

Author’s Response

The relationship between the discussion of international literature and the title of your research, "Towards Net-Zero Emissions from Urban Transport: Ex Post Policy Evaluation in Canberra, The Australian Capital Territory," remains unclear. It is important to clarify how this section supports or aligns with the study's specific focus on Canberra and net-zero emissions in urban transport.

The clarification is as follows. It is clear that to get to net zero emissions in the transport sector requires a multi-pronged government policy package. Over time The international literature review trawled the academic literature so we could accumulate these as a “bench mark” against which have been applied in the ACT. We note that all types of policy identified have be applied in Canberra.

The distinction between the studies reviewed in section 3.1 and section 3.2 appears to be based mainly on the presence of the keyword "Australian." However, it is not clear if there are significant differences in the research content or conclusions of these studies. If no such differences exist, it becomes difficult to understand the relevance of these sections to the overall scope of the study.

We have separated out Australian studies to ensure we have picked up any policies unique to the local context, in particular Federal Government policies with respect to the automobile industry

Regarding the policies introduced by the ACT Government, more detail is needed on how these policies were collected for review. It is critical to explain the method used to ensure comprehensive coverage of relevant policies, rather than relying on a seemingly random selection, to guarantee the completeness of the policy evaluation.

We have already done this in the revised methodology Section that now reads:

The methodology is to identify and to describe the dominant policies to achieve a carbon neutral transport sector from the international literature and from the domestic Australian literature. Using search engines Google Scholar and SCOPUS and the key words “sustainable transport, 2021-23”, 2067 documents were retrieved of which 224 were substantial scientific contributions. Based on reading the abstracts, 22 papers were identified that focussed on policy, incentives, and implementation. In addition, key words “zero emission transport” entered into the search engine identified 1086 papers of which 698 were extracted. From this list the first 50 abstracts of the academic papers downloaded were scrutinised and the policy mentioned was noted. Within this subset of papers, we are confident that we have identified all policies and regulations directed at achieving net-zero emissions (that is, achieving saturation of possible policies). Twenty-eight of these papers dealt in depth with policy, incentives, and implementation., that form the basis for Table 1. The table is not aimed at a comprehensive compilation, description, and review of the international literature on policies leading towards net-zero emissions in the transport sector. The Australian literature was identified using key words “Australia/net zero emissions/ transport/policy”. We used more than one word at the same time on the search engine. The literature search identified the Australian Federal Government’s higher-level energy policies to achieve net zero emissions by 2030 (n=8).

For the case study of Canberra and the ACT we identified the relevant land-use, transport, and environmental policies contained in consultants’ reports to government from 1963 and the more recent ACT Government policies aimed at achieving net-zero emissions from the transport sector (n=32). Since the development of information technologies, governments post policies and regulations on the world-wide web allowing easy access to researchers. To ensure our identification of all policies and their interpretation are accurate, we invited three senior ACT public servants who were involved with the planning of Canberra from 1964 onwards (see Acknowledgement section) to comment on a draft of this paper, specifically asking as to whether all relevant policies had been identified and whether our interpretation of the effectiveness of these policies were sufficiently robust to convince policy makers of their outcomes in contributing towards the target of net zero emissions from the ACT transport sector. As our informants have been senior public servants that span the decades from the establishment of the National Development Commission in 1957 to the present day, we have asked them to identify any key documents that we had not reviewed. Therefore, we are confident that the data base for our evaluation of all relevant policies is complete.

The policy development cycle within governments [20] contains both policy analysis that examines the impacts, benefits and costs, of policy options to assess the best response to an identified societal problem (ex-ante evaluation) and monitoring that tracks the progress of specific targets, objectives and milestones (ex-post evaluation). Researchers are involved in this process applying systems models to quantitatively estimate benefits and costs. A less common approach by researchers – and the one followed in this paper - is to monitor policy outcomes that evaluates the effectiveness of policy instruments and thereby challenging the merits of government policies, strategies and programs [21: 97]. Governments, on the other hand, want to strengthen “the manner in which its policies and programs are evaluated to improve performance and accountability …” and there are detailed guidelines for public servants to follow [22: 1].

Extracting from these ACT Government guidelines, our assessment process on the ACT Government achieving net-zero emissions in the transport sector aims to answer questions such as: is the policy producing the intended outcomes or any unintended outcomes? has the policy achieved its stated objectives? and is the policy still aligned with government priorities, particularly when circumstances change?  Our ex-post evaluation involves forms of analysis, interpretations (and some judgement) and a comparison between stated objectives, performance indicators and actual results where available as suggested by the ACT Government [22: 3].

The case study identifies and describes in detail the evolution of land-use, transport, and environmental policies and the consultants’ reports to government from 1963 and concentrates on the more recent ACT Government policies aimed at achieving net-zero emissions from the transport sector. The review also identifies the Australian Federal Government’s policies to achieve net zero emissions by 2030. In the ex post evaluation of these policies the methodology involves the analysis of secondary data in the periodic State of the Environment Reports, in consultants’ reports and of primary travel data in the Census of Population Journey-to-Work tabulations. The outcomes and milestones of of this evaluation of ACT policies to achieve net-zero emissions is synthesised and summarised in tabular form (Table 5). The Discussion section suggests four groups of policy packages that might be of wider applicability to governments aiming to achieve net-zero emissions in the transport sector.