Reducing car congestion in cities, Kimberly Nicholas

What might be the most effective way of reducing car congestion in our cities? A team of researchers, from Lund University, in Sweden, searched for the answer from a ton of data. In an shorter version of an article appearing on The Conversation website, Kimberly Nicholas, Associate Professor of Sustainable Science at the university, explains…

OF all the peer-reviewed studies, and cases from practice, looking at the effectiveness of various ways to reduce car use in cities, a team of researchers at Lund University in Sweden looked at 800 published between 2010 and now.

The team’s aim was to help city planners and citizens make well-informed decisions, based on real-world data on innovations ranging from the ‘carrot’ of bike and walk-to-work schemes to the ‘stick’ of removing free car parking.

The ranking that follows reflects cities’ successes not only in terms of measurable reductions in car use, but in achieving improved quality of life and sustainable mobility for their residents.

Introducing a congestion charge was found to be the most effective measure, reducing urban car levels by anywhere from 12 per cent to 33 per cent. Meanwhile, creating car-free streets and separated bike lanes was found to lower car use in city centres by up to 20 per cent.

One of the most important conclusions made by the team was that there there is no single ‘silver bullet’ solution; in other words, the most successful cities typically combine a few different policy instruments.

1. Congestion charges

The most effective measure identified by our research entails drivers paying to enter the city centre, with the revenues generated going towards alternative means of sustainable transport.

London, an early pioneer of this strategy, has reduced city centre traffic by a whopping 33 per cent (here) since the charge’s introduction by the city’s first elected mayor, Ken Livingstone, in February 2003. 

The fixed-charge fee (with exemptions for certain groups and vehicles) has been raised over time, from an initial £5 per day up to £15 since June 2020.

Importantly, 80 per cent of the revenues raised are used for public transport investments.

Other European cities have followed suit, adopting similar schemes after referenda in Milan (here), Stockholm (here) and Gothenburg (here) – with the Swedish cities varying their pricing by day and time.

But despite congestion charges clearly leading to a significant and sustained reduction of car use and traffic volume, they cannot by themselves entirely eliminate the problem of congestion, which persists while the incentives and infrastructure favouring car use remain.

2. Parking and traffic controls

In a number of European cities, regulations to remove parking spaces and alter traffic routes – in many cases, replacing the space formerly dedicated to cars with car-free streets, bike lanes and walkways – has proved highly successful. 

For example, in Norway, Oslo’s replacement of parking spaces with walkable car-free streets and bike lanes was found to have reduced car usage in the centre of the Norwegian capital by up to 19 per cent (here).

3. Limited traffic zones

Rome, traditionally one of Europe’s most-congested cities, has shifted the balance towards greater use of public transport by restricting car entry to its centre at certain times of day to residents only, plus those who pay an annual fee. 

This policy has reduced car traffic in the Italian capital by 20 per cent during the restricted hours and ten per cent (here) even during unrestricted hours when all cars can visit the centre. 

The violation fines are used to help finance Rome’s public transport system.

4. Mobility services for commuters

The most effective ‘carrot-only’ measure identified by our review is a campaign to provide mobility services for commuters in the Dutch city of Utrecht. 

Local government and private companies collaborated to provide free public transport passes to employees, combined with a private shuttle bus to connect transit stops with workplaces. 

This programme, promoted through a marketing and communication plan, was found to have achieved a 37 per cent reduction (here) in the share of commuters travelling into the city centre by car.

5. Workplace parking charges

Another effective means of reducing the number of car commuters is to introduce workplace parking charges. 

For example, a large medical centre in the Dutch port city of Rotterdam (here) achieved a 20-25 per cent reduction in employee car commutes through a scheme that charged employees to park outside their offices, while also offering them the chance to ‘cash out’ their parking spaces and use public transport instead.

This scheme was found to be around three times more effective than a more extensive programme in the UK city of Nottingham (here), which applied a workplace parking charge to all major city employers possessing more than ten parking spaces. The revenue raised went towards supporting the Midlands city’s public transport network, including expansion of a tram line.

6. Workplace travel planning

Programmes providing company-wide travel strategies and advice to encourage employees to end their car commutes have been widely used in cities across Europe. 

A major study, published in 2010, assessing 20 cities across the UK (here) found an average of 18 per cent of commuters switched from car to another mode after a full range of measures were combined – including company shuttle buses, discounts for public transport and improved bike infrastructure – as well as reduced parking provision. 

In a different programme, the English city of Norwich achieved near-identical rates by adopting a comprehensive plan but without the discounts for public transport.

These carrot-and-stick efforts appear to have been more effective than Brighton & Hove’s (here) ‘carrot-only’ approach of providing plans and infrastructure such as workplace bicycle storage, which saw a three per cent shift away from car use.

7. University travel planning

Similarly, university travel programmes often combine the ‘carrot’ of promotion of public transport and active travel with the ‘stick’ of parking management on campus. 

One of the most successful examples highlighted in our review was achieved by the University of Bristol, which reduced car use among its staff by 27 per cent (here), while providing them with improved bike infrastructure and public transport discounts. 

A more ambitious programme in the Spanish city of San Sebastián targeted both staff and students at Universidad del País Vasco. Although it achieved a more modest reduction of 7.2 per cent (here), the absolute reduction in car use was still substantial from the entire population of university commuters.

8. Mobility services for universities

The Sicilian city of Catania used a ‘carrot-only’ approach for its students (here). By offering them a free public transport pass and providing shuttle connections to campus, the city was found to have achieved a 24 per cent decrease in the share of students commuting by car.

9. Car sharing

Perhaps surprisingly, car sharing turns out to be a somewhat divisive measure for reducing car use in cities, according to our analysis. 
Such schemes, where members can easily rent a nearby vehicle for a few hours, have showed promising results in Bremen, Germany (here), and Genoa, Italy (here), with each shared car replacing between 12 and 15 private vehicles, on average.

Their approach included increasing the number of shared cars and stations, and integrating them with residential areas, public transport and bike infrastructure.

Both schemes also provided car sharing for employees and ran awareness-raising campaigns. 

But other studies (here) point to a risk that car sharing may, in fact, induce previously car-free residents to increase their car use. We therefore recommend more research into how to design car sharing programmes that truly reduce overall car use.

10. School travel planning

Two English cities, Brighton & Hove and Norwich, have used (and assessed) the ‘carrot-only’ measure of school travel planning: providing trip advice, planning and even events for students and parents to encourage them to walk, bike or carpool to school, along with providing improved bike infrastructure in their cities. 

Norwich found it was able to reduce the share of car use for school trips by 10.9 per cent using this approach, while Brighton’s analysis (here) found the impact was about half that much.

11. Personalised travel plans

Many cities have experimented with personal travel analysis and plans for individual residents, including Marseille in France (here), Munich in Germany (here), Maastricht in the Netherlands (here) and San Sebastian in Spain (here).

These programmes – providing journey advice and planning for city residents to walk, bike or use (sometimes discounted) public transport – are found to have achieved modest-sounding reductions of six-12 per cent. 

However, since they encompass all residents of a city, as opposed to smaller populations of, say, commuters to school or the workplace, these approaches can still play a valuable role in reducing car use overall. (San Sebastián introduced both university and personalised travel planning in parallel, which is likely to have reduced car use further than either in isolation).

12. Apps for sustainable mobility

Mobile phone technology has a growing role in strategies to reduce car use.

The Italian city of Bologna, for example, developed an app for people and teams of employees from participating companies to track their mobility.
Participants competed to gain points for walking, biking and using public transport, with local businesses offering these app users rewards for achieving points goals.

There is great interest in such ‘gamification’ of sustainable mobility – and at first glance, the data from the Bologna app looks striking. An impressive 73 per cent (here) of users reported using their car ‘less’. 

But, unlike other studies which measure the number or distance of car trips, it is not possible to calculate the reduction of distance travelled or emissions from this data, so the overall effectiveness is unclear. 

For example, skipping one short car trip and skipping a year of long driving commutes both count as driving ‘less’.

While mobility data from apps can offer valuable tools for improved transport planning and services, good design is needed to ensure that ‘smart’ solutions actually decrease emissions and promote sustainable transport, because the current evidence is mixed (here).

In conclusion, reducing car dependency is not just a nice idea. 

It is essential for the survival of people and places around the world, which the recent Intergovernmental Panel on Climate Change report on climate impacts (here) makes clear hinges on how close to 1.5°C the world can limit global warming. 

Avoiding irreversible harm and meeting their Paris Agreement obligations (here) requires industrialised nations such as the UK and Sweden to reduce their emissions by ten-to-12 per cent per year (here) – about one per cent every month.

Yet, until the COVID-19 pandemic struck, transport emissions in Europe were steadily increasing. Indeed, current policies are predicted to deliver transport emissions in 2040 that are almost unchanged from 50 years earlier (here).

To meet the planet’s health and climate goals, city governments need to make the necessary transitions for sustainable mobility by, first, avoiding the need for mobility (see Paris’s 15-minute city – here), second, shifting remaining mobility needs from cars to active and public transport wherever possible; and, finally, improving cars to be emissions-free.

This transition must be fast and fair: city leaders and civil society need to engage citizens to build political legitimacy and momentum for these changes. 

Without widespread public buy-in to reduce cars, the EU’s commitment to deliver 100 climate-neutral cities in Europe by 2030 (here) looks a remote prospect.

Radically reducing cars will make cities better places to live – and it can be done. 

A 2020 study (here\) demonstrated that we can provide decent living standards for the planet’s projected ten billion people using 60 per cent less energy than today (here).

But to do so, wealthy countries need to build three times as much public transport infrastructure as they currently possess, and each person should limit their annual travel to between 5,000 kilometres (in dense cities) and 15,000 kilometres (in more remote areas).

The positive impact from reducing cars in cities will be felt by all who live and work in them, not least in the form of more convivial spaces.

Kimberly Nicholas is Associate Professor of Sustainable Science at Lund University, Sweden. @KA_Nicholas

A longer version of this article appears on the website, The Conversation, here.

Pictured: Edinburgh’s by-pass, potentially a congestion charge boundary to the capital, Picture credit: Place Design Scotland

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