--- title: 6 Cities That Got Traffic Control Right, and What Made the Difference description: London, Stockholm, Singapore, Pittsburgh, San Francisco and Los Angeles cut congestion measurably. What each did, the results, and what made it work. image: https://blog.goodvisionlive.com/hubfs/blog-header-6-cities-traffic-control.png --- ###### Stay in touch ### Subscribe to Newsletter Get latest updates and news about GoodVision directly to your inbox. 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Road pricing cut the traffic entering city centers by 18% to 44%. Adaptive and synchronized signals cut travel times by 12% to 25% for the traffic that remained. The six cases below are the ones where a city or its evaluators counted traffic before the change, counted it again afterward, and put the numbers in public. That rules out plenty of well-known smart city programs. Many publish goals, pilots and dashboards but no measured outcome, and a program without a baseline can't show it worked. ## Which cities measurably reduced congestion? | City | Intervention | Measured change | Period | Source | | --- | --- | --- | --- | --- | | London | Central London Congestion Charge (2003) | Traffic entering the zone down 18%, congestion inside the zone down 30% | 2003 vs 2002 surveys | [TfL Impacts Monitoring, Second Annual Report (2004)](https://content.tfl.gov.uk/impacts-monitoring-report-2.pdf) | | Stockholm | Congestion charge (trial 2006, permanent 2007) | Traffic across the cordon down about 22%, congestion down 30% to 50% | 2006 to 2013 vs 2005 | [Eliasson, KTH, CTS Working Paper 2014:7](https://transportportal.se/swopec/cts2014-7.pdf) | | Singapore | Area Licensing Scheme (1975) | All vehicles entering the restricted zone in the morning peak down 44%, cars down 73% | March vs October 1975 | [World Bank Staff Working Paper No. 281 (1978)](https://documents1.worldbank.org/curated/en/883181468759586286/pdf/multi0page.pdf) | | Pittsburgh | Surtrac adaptive signals, 9-intersection pilot (2012) | Travel time down more than 25%, wait time down more than 40%, stops down more than 31% | March vs June 2012 | [Smith et al., Carnegie Mellon, ICAPS 2013](https://www.cmu.edu/traffic21/pdfs/6054-30129-1-pb.pdf) | | San Francisco | SFpark demand-responsive parking pricing (2011) | Vehicle miles traveled in pilot areas down 30%, vs 6% in control areas | Spring 2011 vs spring 2013 | [SFMTA, SFpark Pilot Project Evaluation Summary (2014)](https://www.sfmta.com/sites/default/files/reports-and-documents/2018/04/sfpark_eval_summary_2014.pdf) | | Los Angeles | ATSAC signal synchronization (citywide by 2013) | Travel time down 12%, travel speed up 16% | Before and after studies, 1997 to 2013 | [LADOT, Los Angeles Signal Synchronization fact sheet (2016)](https://ladot.lacity.gov/sites/default/files/documents/ladot-atsac-signals-_-fact-sheet-2-14-2016.pdf) |   ![Bar chart of measured congestion results in six cities. Road and parking pricing cut traffic by 18 to 44%: Singapore 44%, San Francisco 30%, Stockholm 22%, London 18%. Signal control cut travel times by 12 to 25%: Pittsburgh 25%, Los Angeles 12%.](https://blog.goodvisionlive.com/hs-fs/hubfs/insight-1-pricing-vs-signals.png?width=1920&height=1080&name=insight-1-pricing-vs-signals.png) The rows measure different things. Pricing figures count vehicles. Signal figures time the trips of vehicles already on the road. SFpark's figure covers miles driven while circling for a parking space, not all traffic. Read them as six different levers, not a league table.   ## What did each city actually do? **London** charged vehicles for entering a central zone during weekday hours. Cars and minicabs entering the zone fell by a third in the first year, and buses absorbed most of the displaced trips. Transport for London also managed the Inner Ring Road to carry the traffic that went around the zone. **Stockholm** put a time-varying charge on every crossing into the inner city. Traffic dropped from the first day. The response also strengthened over time, as people found more permanent ways to adapt their trips. **Singapore** made drivers buy a license to enter the central area in the morning peak, and exempted car pools. The share of cars carrying four or more people rose from under 10% to 44%. When a new peak formed just after the charged window, the government extended the hours two months in. **Pittsburgh** replaced signal plans computed offline with signals that plan themselves. Each Surtrac intersection builds its own timing from the vehicles approaching it, then shares that plan with its neighbors, several times a minute. **San Francisco** priced parking by block using occupancy sensors. Where a block ran 80% to 100% full, meter prices went up 25 cents. Where it ran 30% to 60% full, they came down. SFMTA repeated the adjustment roughly every eight weeks, aiming for 60% to 80% occupancy, so drivers spent less time circling. **Los Angeles** connected every signal in the city to a central system fed by in-road detectors, which adjusts green time to live volumes and keeps signals synchronized along major corridors. ## What made the difference? Five patterns hold across the evidence. 1. **Pricing moved volumes. Signals moved delay.** Only the charging schemes reduced how many vehicles entered an area. Signal systems made the existing traffic flow better. A city needs to know which problem it has before it picks a lever. 2. **Every credible result had a measured baseline.** SFpark compared pilot areas with control areas. Singapore's evaluators set up before and after surveys a year ahead. Stockholm compared each month with the same month in 2005. The programs that couldn't be included here are the ones that never published a before count. 3. **Gains last only while the lever stays in place.** When Stockholm's trial charge ended in 2006, traffic rebounded almost to its old level until the charge returned permanently in 2007. 4. **Traffic moves to the edges.** In Singapore, traffic in the half hour before the charged window rose 23% and speeds on the ring road fell. London saw small increases on its Inner Ring Road. A before and after that counts only inside the scheme misses this. 5. **The best schemes kept adjusting from data.** SFpark repriced every eight weeks. Singapore extended its hours after seeing the new peak. Surtrac replans continuously. None of them treated launch day as the finish line. ## Did the results last? Not always, and the sources say so plainly. London is the clearest case. Traffic stayed down, with vehicles entering the zone 21% below 2002 levels in 2007. Congestion did not. By 2007, [TfL's sixth monitoring report](https://content.tfl.gov.uk/central-london-congestion-charging-impacts-monitoring-sixth-annual-report.pdf) found congestion in the zone back to its 2002 level. ![ Line chart of the Central London Congestion Charge against 2002 levels. Traffic entering the zone fell 18% in 2003 and was still down 21% in 2007. Congestion inside the zone fell 30% in 2003 but was back to its 2002 level by 2007.](https://blog.goodvisionlive.com/hs-fs/hubfs/insight-2-london-congestion.png?width=1920&height=1080&name=insight-2-london-congestion.png) TfL attributes this to road space given over to buses, pedestrians and public realm schemes, and to a sharp rise in utility roadworks. The freed capacity got used for other things. Other results come with limits too. Pittsburgh's figures come from a 9-intersection pilot, measured by the team that built the system. SFMTA notes that its pilot coincided with the recovery from the recession. LADOT's own fact sheet says that "no traffic signal system is capable of 'fixing traffic.'" These caveats make the results more useful, not less. They show what each intervention can and can't be expected to do. ## How can a city show its own traffic control is working? Count before, count after, and count at the edges. Each of these six results depends on traffic data collected under the same conditions on both sides of the change, over enough time to see whether the effect holds. That's the part most programs skip, and it's the part existing cameras can now cover. GoodVision turns the video from cameras a city already runs into counts, classifications, speeds and travel times, so the baseline exists before the intervention goes in and the follow-up survey uses the same method. See how Telelink City used it for [real-time traffic monitoring in Stara Zagora](https://casestudies.goodvisionlive.com/case-study-real-time-traffic-monitoring-for-congestion-prevention), or read more on [the ripple effect of congestion in cities](https://blog.goodvisionlive.com/the-ripple-effect-of-traffic-congestion-in-cities) and [intelligent traffic management](https://blog.goodvisionlive.com/intelligent-traffic-management-the-secret-of-smart-cities). Planning a change and need the before and after to stand up? [Request a demo](https://goodvisionlive.com/request-demo/) and we'll show you what the measurement looks like on your own footage. [![Three steps to show your traffic control is working: count before the change, count after with the same method, and count at the edges. Includes a Request a demo button, next to a photo of traffic cameras on a street pole.](https://blog.goodvisionlive.com/hs-fs/hubfs/insight-3-article-ending-v4.png?width=1920&height=1080&name=insight-3-article-ending-v4.png)](https://goodvisionlive.com/request-demo/)     Tags: [traffic control](https://blog.goodvisionlive.com/tag/traffic-control), [smart city](https://blog.goodvisionlive.com/tag/smart-city) [Back to Blog](https://blog.goodvisionlive.com) ## Related Articles ## [How Cities Around the World are Improving Traffic Control](https://blog.goodvisionlive.com/how-cities-around-the-world-are-improving-traffic-control) Traffic congestion is a common problem in cities around the world, causing frustration to drivers,... [Read More](https://blog.goodvisionlive.com/how-cities-around-the-world-are-improving-traffic-control) ## [Why Cities Delay Adopting Real-Time Traffic Monitoring Software](https://blog.goodvisionlive.com/why-cities-delay-adopting-real-time-traffic-monitoring) Summary Cities delay adopting real-time traffic monitoring software mainly over integration risk... [Read More](https://blog.goodvisionlive.com/why-cities-delay-adopting-real-time-traffic-monitoring) ## [6 Ways ANPR Supports Smart Traffic Management](https://blog.goodvisionlive.com/6-ways-anpr-supports-smart-traffic-management) Worldwide, urban planners are looking for ways to develop their cities, seeking opportunities for... 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