Ridership vs coverage: The transport planner’s dilemma

Berlin. Image: Getty.

Is your transit agency succeeding? It depends on what it’s trying to do – and most transit agencies haven’t been given clear direction about what they should be trying to do.  Worse, they’re told to do contradictory things.  It’s as if you told your taxi driver to turned left and right at the same time, and then criticised them for turning the wrong direction.

On the one hand, we expect transit agencies to pursue a goal of ridership.  Yet we also demand that provide a little service to everyone, which is called a coverage goal.  The coverage goal requires an agency to run predictably low-ridership services, for non-ridership reasons, so it’s the opposite of a ridership goal

In the fictional town below, the little dots indicate dwellings and commercial buildings and other land uses. The lines indicate roads, and the 18 buses indicate the resources the town has to run transit. Most of the activity in the town is concentrated around a few roads, as in most towns.

A transit agency pursuing only a ridership goal would focus service on the streets where there are large numbers of people – where walking to transit stops is easy, and where the straight routes feel direct and fast to customers. Because service is concentrated into fewer routes, frequency is high and a bus is always coming soon.

This would result in a network like the one below.

All 18 buses are focused on the busiest areas. Waits for service are short but walks to service are longer for people in less populated areas. Frequency and ridership are high, but some places have no service.

Why is this the maximum ridership alternative? It has to do with the non-linear payoff of both high density and high frequency, as explained more fully here.

If the town were pursuing only a coverage goal, on the other hand, the transit agency would spread out services so that every street had a bus route, as in the network at below. Spreading it out sounds great – but it also means spreading it thin.

The 18 buses are spread around so that there is a route on every street. Everyone lives near a stop – but every route is infrequent, even those on main roads, and waits for service are long. Only a few people can bear to wait so long, so ridership is low.

In these two scenarios, the town is using the same number of buses. These two networks cost the same amount to operate, but they deliver very different outcomes.

Ridership-oriented networks serve several popular goals for transit, including:

  • Reducing environmental impact through lower Vehicle Miles Travelled;
  • Achieving low public subsidy per rider, through serving the more riders with the same resources, and through fares collected from more passengers;
  • Supporting continued urban development, at higher densities, without being constrained by traffic congestion;
  • Reducing the cost of for cities to build and maintain road and bridges by replacing automobile trips with transit trips, and by enabling car-free living for some people living near dense, walkable transit corridors.

On the other hand, coverage-oriented networks serve a different set of goals, including:

  • Ensuring that everyone has access to some transit service, no matter where they live;
  • Providing lifeline access to critical services for those who cannot drive;
  • Providing access for people with severe needs;
  • Providing a sense of political equity, by providing service to every municipality or electoral district.

Ridership and coverage goals are both laudable, but they lead us in opposite directions. Within a fixed budget, if a transit agency wants to do more of one, it must do less of the other.

Because of that, cities and transit agencies need to make a clear choice regarding the Ridership-Coverage trade off. In fact, we encourage cities to develop consensus on a Service Allocation Policy, which takes the form of a percentage split of resources between the different goals.


For example, an agency might decide to allocate 60 percent of its service towards the Ridership Goal and 40 percent towards the Coverage Goal.

Major network redesigns often shift this balance, intentionally and consciously.  When we led a redesign of the bus network in Houston, we led a discussion with the elected leaders about their priorities, and they decided to shift the focus of their network from 80 per cent coverage to 5per cent coverage. They knew in advance what the result would be: a more useful network, with the potential to grow more ridership, but also many angry people in areas no longer served.

What about your city? What do you think should be the split between ridership and coverage? The answer will depend on your preferences and values.  For cities, it should be up to elected officials, informed by the public, to decide.

Jarrett Walker is an international consultant in public transit network design and policy, based in Portland, Oregon. Christopher Yuen is an associate at Jarrett Walker+Associates.

Walker is also the author of “Human Transit: How clearer thinking about public transit can enrich our communities and our lives". This article was originally written for his blog, and is reposted here with permission

 
 
 
 

When should you forget the bus and just walk?

Might as well talk, tbh. Image: Getty.

It can often be tempting to jump on a bus for a short journey through the city, especially when it’s raining or you’re running behind schedule. Where there are dedicated bus lanes in place, it can feel as though you speed past gridlocked traffic. But as city authorities begin new initiatives to get people walking or cycling, that could all change – and so could you.

British people are wasting tens of hours in traffic every year: London comes top, with the average commuter spending 74 hours in traffic, followed by Manchester, with 39 hours and Birmingham and Lincoln, both with 36 hours.

It might surprise some people to learn that cities are intentionally slowing down private vehicles, in order to shift people to other, more efficient, modes of transport. In fact, Transport for London removed 30 per cent of the road capacity for private vehicles in central London between 1996 and 2010. That trend continues today, as the organisation gives over more space for buses, cyclists and pedestrians.

London’s road capacity, over time. Image: Transport for London/author provided.

Clamp down on cars

The loss of road capacity for cars has occurred across most UK cities, but not on the same scale everywhere. The good news is that the changes, when made, appear to have reduced actual car congestion. It seems that by making it less attractive to use your car, you’ll be more likely to use other transport. In fact, the average speed of buses and cyclists can be up to twice as fast as normal traffic in cities such as London.

The relationship between walking and improved health has been proven to such an extent that it seems everyone – your doctor, your family, regional and national government – wants to increase physical activity. The savings in health care costs, are via improved fitness, reduced pollution and improved mental health, and its impact on social care are huge.

For instance, Greater Manchester wants to increase the number of people who get the recommended level of exercise (only about half currently do). The most advanced of these plans is London’s, which has the specific goal of increasing the number of walks people take by a million per day.

So, the reality is that over the next few years, walking will gradually appear more and more “normal” as we are purposefully nudged towards abandoning our rather unhealthy, sedentary lifestyles.


The long journey

Consider this: the typical bus journey in the UK is almost three miles, with an average journey time of around 23 minutes. The equivalent walk would take approximately 52 minutes, travelling at just over three miles per hour. It seems obvious that the bus is much faster – but there’s much more to consider.

People normally walk at least a quarter of a mile to and from the bus stop – that’s roughly ten minutes. Then, they have to wait for a bus (let’s say five minutes), account for the risk of delay (another five minutes) and recover from the other unpleasant aspects of bus travel, such as overcrowding.

This means that our 23 minute bus journey actually takes 43 minutes of our time; not that much less than the 52 minutes it would have taken to walk. When you think of the journey in this holistic way, it means you should probably walk if the journey is less than 2.2 miles. You might even choose to walk further, depending on how much value you place on your health, well-being and longevity – and of course how much you dislike the more unpleasant aspects of bus travel.

The real toss up between walking and getting the bus is not really about how long it takes. It’s about how we change the behaviour and perceptions we have been conditioned to hold throughout our lives; how we, as individuals, engage with the real impacts that our travel decisions have on our longevity and health. As recent converts to walking, we recommend that you give it a go for a month, and see how it changes your outlook.

The Conversation

Marcus Mayers, Visiting Research Fellow, University of Huddersfield and David Bamford, Professor of Operations Management, University of Huddersfield.

This article is republished from The Conversation under a Creative Commons license. Read the original article.