Travel Time’s Constant Companion: How High-Speed Rail Redefines the Commute

Marchetti's Constant and High-Speed Rail (HSR): Bridging Urban Planning and Mobility

Marchetti’s Constant—the idea that humans spend on an average, one hour per day traveling—has profound implications for urban planning and transport infrastructure. This "travel time budget" shapes how cities evolve, determining everything from the layout of neighbourhoods to the modes of transport we prioritize.

Is there any relationship with this "travel time budget” with the Cost-benefit analysis framework to justify the investment in High-Speed Rail (HSR) project, as a transformative transport mode in the context of this principle?

The Role of Marchetti’s Constant in Urban Planning

1.?Travel Time as a Constant: Urban areas naturally expand as transport technologies improve. Faster modes of transport, such as cars or trains, enable people to live farther from their workplaces or urban centres, while still maintaining their one-hour travel time on an average.

2. Urban Sprawl and Inequality: In cities designed around cars, longer commutes lead to urban sprawl, often marginalizing low-income populations who cannot afford housing close to city centres.

This constant can partially explain the spatial dynamics of slums. People in urban slums prioritize living close to employment centres, often sacrificing housing quality for reduced travel time and costs. Lack of affordable, efficient public transport forces individuals to live within walking distance of jobs, leading to higher concentrations of informal settlements near city centres or industrial zones.

3. The Need for Compact Growth: Marchetti's constant suggests that well-connected, transit-oriented development can curb sprawl, creating denser cities where people travel efficiently without exceeding the one-hour budget.

How HSR Reshapes the Constant

1.?Shrinking Distances, Expanding Choices: High-Speed Rail redefines urban and regional relationships by dramatically reducing travel times between cities. For example:

o?? A 500-kilometer journey that takes 4–5 hours by car or conventional train can be reduced to under 2 hours by HSR.

o?? Commuters can live in smaller towns or rural areas while accessing urban job markets, reshaping the concept of "commuter belts."

Rail infrastructure is more than mobility—it’s a powerful tool for economic inclusion. Subsidized fares, job creation through rail projects, and equitable access to rail services can act as economic buffers, lifting vulnerable populations.

High-speed rail, metro systems, and regional links stimulate growth, bridge economic disparities, and connect underserved communities, making rail a cornerstone of equitable urban and regional development.

2. Regional Redistribution of Growth:

o??Positive Impact: HSR spreads urban opportunities across regions, reducing pressure on overburdened city centres.

o??Risk of Imbalance: Without equitable policies, HSR may exacerbate inequalities, concentrating wealth and jobs in already prosperous urban hubs.

3. Marchetti’s Constant in Action: HSR aligns with Marchetti’s principle by expanding the geographic reach of the one-hour travel bubble, allowing cities to grow sustainably without excessive commute times.

HSR’s Role in Mitigating Urban Sprawl

o??Promoting Polycentric Development: HSR encourages the growth of secondary cities, creating "polycentric" regions where people can live, work, and access services across multiple urban hubs. Examples include the Tokyo-Osaka corridor in Japan and the Paris-Lyon axis in France.

o??Sustainability Benefits: Compact, transit-oriented development supported by HSR reduces reliance on cars, lowering emissions and preserving green spaces.

o??Integration with Urban Planning: To maximize benefits, HSR must integrate with local transit (e.g., metros, buses) and resolve last-mile challenges, ensuring seamless connectivity.

Challenges in Aligning HSR with Marchetti’s Constant

Affordability and Accessibility: HSR fares must remain competitive to ensure equitable access for all income groups, avoiding a system that benefits only high-income commuters.

Land Use Policies: Urban planning must prevent "HSR-enabled sprawl," where stations built in rural areas lead to unsustainable growth patterns.

Environmental Considerations: While HSR reduces travel time, the energy and resources required to build and maintain these networks must align with sustainability goals.

Why Choose High-Speed Rail (HSR) Over Other Modes of Transportation? Is It the Right Fit for Australia?

From a policymaker's perspective, the primary goal is to shift the modal split in passenger transport to reduce urban congestion, minimize accidents, and mitigate environmental impacts. High-Speed Rail (HSR) offers a promising solution, steering the modal split in favour of railways.

Beyond addressing mobility, HSR can promote economic inclusion, acting as an economic buffer by providing affordable, efficient transport that helps lift vulnerable populations closer to the minimum earning threshold.

What is Modal Split?

Also known as Modal Share or Mode Split, Modal Split refers to the percentage of travellers using a specific mode of transportation, or the number of trips made using that mode. It serves as a critical tool for analysing travel behaviour and understanding the distribution of transportation usage. Modal Split is typically expressed in metrics like passenger-kilometers or tonne-kilometers.

However, post-COVID data could suggests a possible shift toward greater public transport use, driven by rising fuel prices and increased investment in rail infrastructure.

Australia's modal split reveals a heavy reliance on private vehicles, reflecting the country's expansive geography and historically car-centric urban planning. Public transport, rail freight, and non-motorized modes occupy smaller shares of the transportation mix, though significant efforts are underway to shift toward greener, more efficient options.

Marchetti's constant reminds us that travel time, not distance, is the key determinant of urban growth. High-Speed Rail, by dramatically reducing travel times, aligns perfectly with this principle, enabling smarter, more sustainable urban planning. Additionally, the average willingness to pay among potential users suggests a readiness to adopt such transformative transport solutions.

However, the critical question remains: “Do the social benefits of HSR—such as reduced congestion, improved accessibility, and economic inclusion—justify the high investment required to build and maintain it?”