Editing London congestion charge (section)

== Effects ==
A number of studies have been made of its effects on congestion, traffic levels, road safety, the use of public transport, the environment, and business activity matters. 

One such study concluded that these effects cannot be causally attributed to the congestion charge, as the trends in these factors began before the introduction of the congestion charge, and continued largely unchanged after the introduction of the charge.<ref name="results2012"/>

=== Traffic changes ===

====Traffic volume====
[[File:London congestion cars 2008.png|thumb|Changes in the counts of cars and taxis in London at October 2008 compared to October 2001. Red dots show reductions and blue dots increases. The boundary of the congestion charge is shown in yellow.]]
[[File:London congestion cycles.png|thumb|Changes in the counts of bicycles at October 2008 compared to October 2001. Red dots show reductions and blue dots increases.]]

A year before the congestion zone, TfL set up automatic traffic counters and augmented them with regular classified traffic counts at key locations, to monitor flows.<ref name=tfljune2007/>

TfL's report in June 2007 found that the number of chargeable vehicles entering the zone had reduced by 30% (primarily cars and minicabs, although vans and lorries had decreased by 13%), while there were overall increases in the numbers of taxis, buses, and especially bicycles. The daily profile of traffic flows had changed, with less traffic after 9:30&nbsp;am and a peak immediately before and after the end of the charging period. The level of traffic entering the zone during the morning peak had not reduced as much as at other times.<ref name="tfljune2007" /> The overall level of traffic of all vehicle types entering the central Congestion Charge Zone was consistently 16% lower in 2006 than the pre-charge levels in 2002.<ref name="tfljune2007" /> Year on year, counts of inbound traffic approaching the zone had also seen a distinct and significant 5–7% decline in the number of chargeable vehicles, which was unexplained.<ref name="tfljune2007" /> They had noted a small but pervasive long-term trend of less traffic entering the zone, expected to be a result of people changing their location and lifestyle, perhaps influenced by the charge. The conservative [[Bow Group]] noted that the main effect occurred after 11&nbsp;am.<ref name="bow"/><!-- The Bow Group report commented on Fig 2.2 from the TFL report (page22). Would be nice to have that graph here. -->

Once within the charging zone car and delivery traffic remained unchanged, suggesting that the journeys made by residents and businesses within the zone were broadly unaffected. Changes to the road network over the years has made direct comparisons difficult, but TfL suspect that certain routes used heavily by taxis and buses within the zone have seen substantially increased traffic. On some of the boundary roads traffic numbers had increased slightly but congestion and delays were largely unchanged from 2002 levels.

Following the introduction of the Western Extension, TfL stated that traffic had fallen around 10 to 15% in the extended zone.<ref name="bbc20070521" /> The original zone showed a 4% increase in congestion, following expansion of the congestion charging area and the introduction of discounts extended to residents of the new zone and buffer zone.<ref name="bbc20070711">{{cite news |url=http://news.bbc.co.uk/1/hi/england/london/6292930.stm |date=11 July 2007 |title=Road toll 'cut traffic by 70,000' |work=BBC News |access-date=24 November 2007 |archive-url=https://web.archive.org/web/20150429041145/http://news.bbc.co.uk/2/hi/uk_news/england/london/6292930.stm |archive-date=29 April 2015 |url-status=live}}</ref> TfL assessed the increase in charges in 2005 to have had only a slight impact overall.<ref name="tfljune2007" />

In February 2013, ten years after the scheme introduction, TfL reported a 10% reduction in traffic levels from baseline conditions.<ref name=Guardian012014/> TfL assessed that the scheme has had a significant impact in shifting people away from using cars, contributing to an overall reduction of 11% in vehicle kilometres in London between 2000 and 2012.<ref name=2014assessment/>

A 2024 study found that the congestion charge reduced traffic in downtown London, as well as on untolled suburban roads leading downtown.<ref name=":1">{{Cite journal |last=Herzog |first=Ian |date=2024 |title=The city-wide effects of tolling downtown drivers: Evidence from London's congestion charge |url=https://www.sciencedirect.com/science/article/abs/pii/S0094119024000846 |journal=Journal of Urban Economics |volume=144 |pages=103714 |doi=10.1016/j.jue.2024.103714 |issn=0094-1190}}</ref> The study found that the charge had a progressive impact, as low-skill commuters in the suburbs benefitted from less traffic.<ref name=":1" />

====Traffic speeds====
The charge operates for under one third of the hours in a year and covers around two-thirds of the central London traffic.<ref name="tfljune2007" /> In total 8% of traffic kilometres (miles) are affected by the scheme.<ref name="tfljune2007" /> TfL have extrapolated the trends in road speed in the congestion zone; they have suggested that speeds would have dropped from 17&nbsp;km/h (10&nbsp;mph) in 2003 to 11.5&nbsp;km/h (7&nbsp;mph) by 2006, had the scheme not been put in place.<ref name="tfljune2007" />

A report by TfL in early 2007 indicated that there were 2.27 traffic delays per kilometre (3.65 per mile) in the original charging zone. This compared with a figure of 2.3 per kilometre (3.7 per mile) before the introduction of the congestion charge. After the scheme was introduced they had measured an improvement in journey times of 0.7 minutes per km (1.1 per mile), or 30%. This improvement had decreased to 22% in 2006, and during 2006 congestion levels had increased so that the improvement, compared to the year before the scheme, was just 7%. TfL explained this as a result of changes to road priorities within the zone, delays caused by new pedestrian and road user safety schemes, and, most particularly, a doubling of road works in the latter half of 2006.<ref>{{cite news |url=http://news.bbc.co.uk/1/hi/england/london/7109727.stm |title=Congestion charge 'not working' |date=23 February 2007 |work=BBC News   |access-date=23 November 2007 |archive-url=https://web.archive.org/web/20150429041334/http://news.bbc.co.uk/2/hi/uk_news/england/london/7109727.stm |archive-date=29 April 2015 |url-status=live}}</ref> Utilities were encouraged to complete planned road works in the year preceding the congestion charge, so it would appear that the first year of measurement used for later comparisons would also have been affected by streetworks to some extent.<ref name="bbc20070711" /><ref>{{Cite news |url=https://www.telegraph.co.uk/news/uknews/1454446/London-congestion-charge-not-working.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/news/uknews/1454446/London-congestion-charge-not-working.html |archive-date=12 January 2022 |url-access=subscription |url-status=live |title=London congestion charge 'not working' |first=Paul |last=Marston |work=The Daily Telegraph |date=16 February 2004 |access-date=24 November 2007}}{{cbignore}}</ref>

TfL reported in January 2014, that despite a reduction of traffic volume within London, traffic speeds have also been getting progressively slower over the past decade, particularly in central London. TfL explains that the historic decline in traffic speeds is most likely due to interventions that have reduced the effective capacity of the road network to improve the urban environment, increase road safety and prioritise public transport, pedestrian and cycle traffic, as well as an increase in road works by utilities and general development activity since 2006. This explains the lower levels of congestion reduction compared to the pre-charge baseline: 8% in 2006, compared to 30% in 2004. Since 2006 this trend towards slower traffic movement has ceased and traffic speeds have remained more stable, as evidenced by GPS satellite tracking data from 2006 to 2012. Indicators of excess delay or congestion also suggest a stable overall picture, with some improvements in the past two years. TfL concludes that while levels of congestion in central London are close to pre-charging levels, the effectiveness of the congestion charge in reducing traffic volumes means that conditions would be worse without the Congestion Charging scheme.<ref name=2014assessment/>

=== Air quality ===
The pre-commencement report from TfL noted that the scheme was not expected to significantly affect [[air quality]], but that offering a discount to encourage the use of greener fuels would be a positive measure.<ref name="tflprereport" />

TfL reported that levels of [[nitrogen oxides]] (NO<sub>X</sub>), fell by 13.4% between 2002 and 2003, and carbon dioxide, as well as the levels of [[Atmospheric particulate matter|airborne particulates]] (PM10) within and alongside the [[Inner Ring Road, London|Inner Ring Road]] boundary of the zone.<ref name="tfljune2006" />

Since 2002, the [[nitrogen dioxide]] (NO<sub>2</sub>) produced by [[diesel exhaust]] has become a serious problem, with the [[London Air Quality Network]] of [[Imperial College]] reporting that the annual mean NO<sub>2</sub> objective (of 40 μgm-3 or 21 ppb) was exceeded at all kerbside and roadside monitoring sites across central and greater London during 12 months between 2005 and 2006.  Although no areas within the Congestion Charge Zone reported NO<sub>2</sub> levels above an upper limit of 200 μgm-3 (105 ppb), some monitoring areas near the zone boundary experienced very long periods at such levels, notably the [[A23 road|A23]] near Brixton (3741 hours) and the [[Marylebone Road]] (849 hours).<ref name=laqn>{{cite web |url=http://www.londonair.org.uk/london/reports/AirQualityInLondon2005andmid2006.pdf |title=Air Quality in London 2005 and mid 2006 – Briefing |last=Fuller & Green |date=28 July 2006 |publisher=London Air Quality Network |access-date=8 January 2008}}</ref>

In 2007, the ''Fifth Annual Monitoring Report'' by TfL stated that between 2003 and 2006, NO<sub>X</sub> emissions fell by 17%, PM10 by 24% and CO<sub>2</sub> by 3%, with some being attributed to the effects of reduced levels of traffic flowing better, with the majority being as a result of improved vehicle technology.<ref name="tfljune2007" /><ref name="glareport">{{cite web |url=http://www.airquality.co.uk/archive/reports/cat09/0505171128_London_Congestion_Charge_Detailed_Assessment.doc |first=Lucy |last=Sadler |title=Detailed assessment London congestion charging |format=DOC |access-date=20 January 2008 |publisher=UK Air Quality Archive|archive-url = https://web.archive.org/web/20080228180759/http://www.airquality.co.uk/archive/reports/cat09/0505171128_London_Congestion_Charge_Detailed_Assessment.doc |archive-date = 28 February 2008}}</ref> In total, the rate of fall in CO<sub>2</sub> has been almost 20% as of 2007.<ref>{{cite news |title=Milan introduces traffic charge |url=http://news.bbc.co.uk/1/hi/world/europe/7167992.stm |work=BBC News |date=2 January 2008 |access-date=20 January 2008 |archive-url=https://web.archive.org/web/20150429041527/http://news.bbc.co.uk/2/hi/europe/7167992.stm |archive-date=29 April 2015 |url-status=live}}</ref>

The 2007 TfL report makes it clear that only a one-off reduction of emissions could be expected from the introduction of the charge, whilst further reductions are unlikely to be as a result of the charge.  It notes that lower vehicles emissions may not necessarily feed through into improvements in air quality as vehicle emissions are only one contributor to total emissions of a particular pollutant along industrial sources and that weather conditions play a significant role, and that pollutant concentrations were being affected by changes in the make up of the vehicle fleet.  It also suggests that the rate of decline in certain pollutants is decreasing.<ref name="tfljune2007" />

A 2011 independent study published by the [[Health Effects Institute]] (HEI), and led by a researcher from [[King's College London]], found that there is little evidence the congestion charge scheme has improved air quality.  This research used modelling and also compared actual air pollutant measurements within the congestion charge zone with those of control sites located in Outer London.  The investigators concluded that "it is difficult to identify significant air quality improvements from a specific program{{snd}}especially one targeted at a small area within a large city{{snd}}against the backdrop of broader regional pollutant and weather changes."<ref>{{cite web|url=http://www.greencarcongress.com/2011/04/hei-study-finds-london-congestion-charging-scheme-shows-little-evidence-of-improving-air-quality.html#tp |title=HEI study finds London Congestion Charging Scheme shows little evidence of improving air quality|publisher=[[Green Car Congress]]|date=27 April 2011|access-date=22 May 2011}}</ref>  National trends had already shown a rapid decline of some other emissions during the late 1990s, notably [[carbon monoxide]], and levels have been relatively stable since 2002 across London.{{citation needed|date=April 2012}}

A 2020 study of London found that the London congestion charge led to reductions in pollution and reductions in driving, but it increased pollution from diesel taxis and buses (which are exempt from the charge).<ref>{{Cite journal|last1=Green|first1=Colin P.|last2=Heywood|first2=John S.|last3=Navarro Paniagua|first3=Maria|date=2020-09-01|title=Did the London congestion charge reduce pollution?|url=http://www.lancaster.ac.uk/media/lancaster-university/content-assets/documents/lums/economics/working-papers/LancasterWP2018_007.pdf|journal=Regional Science and Urban Economics|language=en|volume=84|pages=103573|doi=10.1016/j.regsciurbeco.2020.103573|bibcode=2020RSUE...84j3573G |s2cid=169274952|issn=0166-0462}}</ref>

{| class="wikitable"
|-
|
| colspan="3" | Charging zone
| colspan="3" | Inner Ring Road
|-
|
| NO<sub>X</sub>
| PM10
| CO<sub>2</sub>
| NO<sub>X</sub>
| PM10
| CO<sub>2</sub>
|-
| Overall traffic emissions change 2003 versus 2002<ref name="tfljune2006" />
| −13.4
| −15.5
| −16.4
| −6.9
| −6.8
| −5.4
|-
| Overall traffic emissions change 2004 versus 2003<ref name="tfljune2006" />
| −5.2
| −6.9
| −0.9
| −5.6
| −6.3
| −0.8
|-
| Changes due to improved vehicle technology 2003-2006<ref name="tfljune2007" />
| −17.3
| −23.8
| −3.4
| −17.5
| −20.9
| −2.4
|-
| colspan="7" style="text-align:center;font-size:90%;"|<small>Source: {{cite web |url=http://www.tfl.gov.uk/cdn/static/cms/documents/FourthAnnualReportFinal.pdf |title=Impacts Monitoring – Fourth Annual Report |publisher= [[Transport for London]] |archive-url=https://web.archive.org/web/20150429042848/http://www.tfl.gov.uk/cdn/static/cms/documents/FourthAnnualReportFinal.pdf |archive-date=29 April 2015 |url-status=live}} and {{cite web |url=http://www.tfl.gov.uk/assets/downloads/fifth-annual-impacts-monitoring-report-2007-07-07.pdf |access-date=23 November 2007 |date=June 2007 |title=Impacts Monitoring – Fifth Annual Report |archive-url=https://web.archive.org/web/20140122090211/http://www.tfl.gov.uk/assets/downloads/fifth-annual-impacts-monitoring-report-2007-07-07.pdf |archive-date=22 January 2014 |publisher=[[Transport for London]] |url-status=live}} 2003–2004 figures are TfL estimates. </small>
|}

=== Public transport ===
On the launch date of the original zone, an extra 300 buses (out of a total of around 8,000) were introduced.<ref name=more_buses/> Bus route changes have been made to take advantage of the presumed higher traffic speeds and the greater demand for public transport; [[London Buses route 452|route 452]] was introduced and three others (routes [[London Buses route 31|31]], [[London Buses route 46|46]] and [[London Buses route 430|430]]) were extended. The frequency of buses on other routes through the zone extension were also increased.<ref>{{cite web |url=https://www.bbc.co.uk/london/content/articles/2007/02/19/congestion_bus_routes_feature.shtml  |publisher=BBC London |access-date=26 May 2007 |title=Buses increased after congestion extension}}</ref>

In 2007 TfL reported that bus patronage in the [[central London]] area (not the same as the Congestion Charge Zone) had increased from under 90,000 pre-charge to stabilise at 116,000 journeys per day by 2007. It also reported that usage of the Underground has increased by 1% above pre-charge levels, having fallen substantially in 2003–2004. They could not attribute any change in [[National Rail]] patronage to the introduction of the central zone charge.<ref name="tfljune2007" />

===Road safety===
TfL estimated that the charge has led to a small reduction in road traffic casualties against a background trend of improvement across London and across [[Reported Road Casualties Great Britain|the rest of Great Britain]] over the period. Cars and motorcycles have seen the biggest reduction in accidents, whereas bicyclists have seen a slight increase, which may reflect their increased numbers.<ref name="tfljune2007" />

Of the reduction from 2,598 personal injury crashes inside the zone in the year before the scheme to 1,629 by 2005 TfL estimated that some 40 and 70 injuries may have been avoided annually due to the introduction of the charging zone, with most of the remaining reduction attributed to other changes to the road network favouring its people-moving capacity.<ref name="tfljune2006" />