Many cities struggle with the increasing motorized individual traffic – especially the fast growing cities of Africa and Asia. Pollution reaches hazardous levels, average speed plummets to less than 10 km/h during rush hours and citizens spend hundreds of ours being trapped in traffic jams, costing billions of dollars every year.

A significant portion of this “too much of traffic” is induced by commuters from these cities outskirts. As living close to work is too expensive for many, they commute every day – and as cars have a much lower capacity than mass transit systems, they cause these issues. Therefore cities around the globe have a vital interest to find ways to keep cars out of their centers and instead provide alternatives. This blog post outlines some of them for commuter traffic. Business and freight traffic are out of scope.

Reducing car traffic in cities was one of the stream in the global 2019 Climathon

How can cities reduce car traffic?

Unfortunately there is no simple answer to this question and each city will likely have a couple of different answers. But there might be some best practices which could help to find the right answer for your city:

Understanding the Root Causes

As for every improvement project defining the problem, measuring the size of the problem and then analyzing the root causes is a good starting point and will likely lead to the most effective actions.

The main cause in most cities will likely and simply be the increasing urbanization. Cities bear most work opportunities, education, higher wages and a better infrastructure than rural areas. Also the ongoing industrialization of agriculture requires less workforce and climate change makes the lives for farmers harder in many areas. As a result many unemployed people from rural areas and their families try their luck in the cities. Gentrification adds on this effect: the city centers or even entire areas like the Silicon Valley become too expensive for large portions of the population. As living close to work is often too expensive, an increasing number of citizens live outside of these areas and commute increasing distances every day.

The root cause of the traffic challenges in most cities is simply the increasing urbanization. Especially in Africa and Asia this trend will lead to huge challenges in the coming decades.
Source/(c): WikiCommons

So what can municipalities do about it? Every area will require their own strategy – and what might work today may be obsolete tomorrow. So finding the “optimal strategy” might be impossible. The only universal truth might be that doing nothing is the worst option of all. Instead applying an agile approach with a broad set of long-term and short-term measures and close monitoring of the results and iterative learning loops might be a reasonable approach.

Long Term Measures

Build more streets?

In the last century urban planners of most cities tried to cope with the increasing car traffic by doing the obvious: they gave the car traffic top priority and increased road capacity again and again. It took a while until scientists realized that on the long run the rebound effect almost always eats up the entire benefits – leading to exactly the same average speed as it was prior to the extension, the so called Braess Paradox. So increasing road capacity as a solution can be ruled out in most cases.

Improve and enforce traffic management

Traffic flow is often hindered by participants entering a crossing when it is not empty – leading to a grid lock. Also stopping or parking on bus and bike lanes or bus stops or second row parking can massively slow down traffic and cause risky situations. Consequent law enforcement is key to avoid this – ideally with automated ticketing systems, such as deployed by the Transport for London (TfL) traffic authority.

Also technology can help to improve traffic flow – both on streets with “green wave” traffic light management and on rails: sensors on “digital” rails allow railway and subway provides to increase the frequency of trains. Other sensors could raise alerts for predictive maintenance and so avoid interruptions.

Mass transit to increase traffic efficiency

Increasing Mass Rapid Transit (MRT) systems such as commuter trains, trams or subways have the beauty that they allow a much higher capacity and traffic density compared to car traffic, which is nicely illustrated in the image below. But be aware of the rebound effect also for this mode of transport. Even the bullet trains and Hyperloop might just increase the distances traveled within a given travel time budget and so induce further traffic, see Marchetti’s Constant.

Visualization of traffic density with different means of transport related to the city of Seattle’s Commuter Toolkit. Courtesy of iSustain.

Urban planning and development

Today most urban development planners have understood that it might be a good idea to create residential areas and hubs where work and education happens outside of the city centers in order to allow for shorter commuting distances. This requires long-term thinking and planning and the inclusion of neighboring communities. Planning time horizons for such measures can easily span up to 30 years – at least in democracies 😉

Short Term Measures

Some measures can be applied without considering long planing cycles:

  • Reduce the need to commute
  • Improve traffic flow
  • Increase traffic density with the given modes of transport

Some examples will be outlined below.

Give Alternatives!

Regardless of what measures will be taken, cities are well-advised to always give reasonable alternatives in case they implement any kind of restrictions or price increases for established means of transport. The violent protests in France and Chile due to minimal prices increases for daily commute have proven its relevance.

Reduce the need to commute

Independent from the pollution, costs and stress commuter traffic causes, nobody wants to waste time being trapped in a traffic jam. So the ultimate paradigm should be reducing the need to commute instead of making commute more efficient.

With an increasing percentage of people working in office jobs and better internet connections, physical presence at work becomes less important and remote work an option. Municipalities could influence this and foster telework / home office days and video conferences. At least some reduction in congestion can already be achieved by more flexible working hours and so reduce traffic peaks.

Analyzing mobility patterns can also unveil eye-opening opportunities: often it can be seen that citizen A commutes to work close to where citizen B lives and vice versa. Both citizens could save time and money and improve their quality of live if they would swap their homes or jobs. Of course it is rarely that simple but the opportunity is huge and the reason why it is often not tapped is simply a lack of information about it. Home swap platforms and campaigns could help tapping this potential and help citizens to live closer to their work or schools.

Better connect the outskirts of a city

Most implementations of MaaS or any kind of smart mobility have shown that they can only operate profitably in high density areas. This leaves the outskirts of a city and even more its periphery and rural areas underserved with mobility services unless highly subsidized by the government. The “mobility desert” often starts already right outside of the city center. Within the perimeters of the city Public Transport (PT) and Transport Service Providers (TSPs) may be enforced to cover this area in a MaaS system as well. But this might not economically be feasible for low density rural areas. For these rural areas feeder traffic will mainly be based on privately owned cars eventually supplemented by public transport buses and some demand-responsive traffic (DRT) such as subsidized on-call taxis or citizens’ shuttle buses, which do not need to operate profitably.

The problematic feeder traffic is the one from the privately owned cars entering the city from its outskirts. Once sitting in a car driving towards the city, drivers are likely to drive their whole way into the city and cause congestion. If cities want to keep out this private feeder car traffic they need to:

  1. Give an alternative with Park & Ride at the city boundaries
  2. Hinder cars from entering the city
Connect a city’s feeder traffic from the periphery with the inner city MaaS and public transport options using Park & Ride mobility hubs
Map courtesy of OpenStreetMap

Sufficient and affordable Park & Ride hubs at the city boundaries are key to keep car traffic out. If this is given further factors will play a role in a commuter’s decision, such as:

  • Speed
  • Costs
  • Convenience
  • Safety
  • Disabilities
  • Transportation of children
  • Transportation of goods
  • Lack of transport options for the return ride

Ideally using the own car in combination with Park & Ride should be the best option for commuters. And sometimes it is the best option – not just known by the commuters. To create this awareness MaaS and navigation systems could help compare these options and nudge commuters to test it.

The image to the left shows a prototype of an app function to compare cost and benefits of driving into the city from the outskirts by car vs. using Park & Ride at the city fringe in combination with MaaS.

Showing these benefits could convince ingrained car drivers to test new ways of commuting.

This Prototype has been developed at the 2019 Climathon. The function could be integrated in all MaaS applications and intermodal route planners. The team which was developing this prototype is happy to share their insights.

Ride Sharing/ Carpooling

Ride sharing or car pooling can help to increase the efficiency of a traffic system via a higher utilization of the empty seats in vehicles already driving a route. The most common ride sharing is not sharing a car or shuttle but sharing a bus, a train, a ferry or plane. This should not be confused with ride hailing, where a taxi-like service drives to the passenger and takes them to their destination. But this is a big enough topic for several blog posts. In short and simplified: ride sharing increases transport efficiency, ride hailing does the opposite.

Pooling could be supported by city authorities by allowing taxis to pool rides and adjust their tariffs accordingly or by fostering car pooling applications and implementing HOV lanes.

HOV and bus lanes

High Occupancy Vehicle (HOV) lanes allow cars to drive on a separate lane when occupied with a minimum number of passengers. Offering this benefit should motivate car drivers to fill their empty seats with other passengers and pool their rides. Bus lanes should also allow buses not to get stuck in traffic jams and so increase the overall traffic system’s efficiency.

Parking space management

Up to one third (!) of the inner city traffic during rush hour is traffic searching for available parking spaces. So parking pace management could be key to congestion management. Consequent parking space management would also leave no doubt that bringing cars to town is costly. If combined with availability management, i.e. keeping track of available parking lots and the option to reserve them, it would make this type of traffic completely redundant and city authorities could mainly control the number of cars entering the city by providing more or fewer parking lots or re-purposing parking laybys/curbside parking lots e.g. as bike lanes.

Congestion fees and car-restricted areas/times

One highly effective measure to reduce inner-city traffic is to either ban cars completely (usually except for taxis, public transport and bikes) from certain areas or at certain times. For drastic measures like this it is important to have alternative modes of transport already in place at the time of implementation.

Job tickets, mobility budgets and perks

Employers may play a key role in traffic avoidance. They could provide positive incentives by offering subsidized public transport flat fees or mobility budgets with efficient transport modes giving a higher priority or offer other perks like shared bikes or safe bike racks and showers for cyclists instead of parking space and so support their employees on the last mile from a train station to the office.

This is just a short list of potential measures to avoid car traffic entering cities from the outskirts. Many of them have been implemented and tested already and the respective cities might be willing to share their experiences.

How to Keep Cars out of Cities
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