Air Quality Impacts of the London Low Emission Zone Ben Barratt, King s College London 49 th IAPSC Conference: Mon 13 th Dec 2010
Identifying the impacts of an LEZ Few, if any, comprehensive LEZ accountability studies Stage 1: How have affected vehicle emissions changed? - Emissions class and volume - How have non-affected vehicle emissions changed? - Does this change vary spatially and temporally? Stage 2: Can these emissions changes be identified in ambient monitoring data after confounding factors are removed? - Meteorology, regional sources, non-transport local sources, independent LAQM measures Stage 3: Can these air quality changes be quantified in health terms? 2
The London Low Emission Zone The primary aim is to reduce PM 10 concentrations across Greater London by targeting the most heavily polluting diesel vehicles. Phased introduction: - Phase 1 (February 2008) HGVs > 12t PM Euro III - Phase 2 (July 2008) HGVs >3.5t, buses and coaches Euro III - Phase 3 (delayed from Oct 2010) LGVs and minibuses - Phase 4 (January 2012?) HGVs, buses and coaches to Euro IV Largest LEZ in the world - covers an area of 2644 km 2 in which more than 8 million people reside. 3
The London LEZ accountability study Detailed emissions modelling. Dedicated pollution monitoring network. Extensive characterised traffic data (ANPR captures). Impacts research programme: Pollutant analysis, including a range of particle metrics, Character and changes in particle toxicity. Tower Hamlets exposure study. GP and hospital admissions health response study. 4
The LEZ impacts monitoring network Supersites placed where modelling predicted greatest impact Augmented Local Authority sites, plus one new site Co-located detailed pollutant and traffic data (ATC, ANPR) Site name, code and location Inner London Marylebone Road, Westminster, Central London ( MY1 ) Parameters monitored PM 10, FDMS PM 10, PM 2.5, P NUM, CBLK, NO X, O 3, meteorology Old Street, Hackney, Central London ( HK6 ) PM 10, NO X, O 3, PM 2.5 Outer London A206 Cray, Bexley, East London ( BX8 ) FDMS PM 10, FDMS PM 2.5, NO X, O 3, meteorology Woolwich Flyover (A2), Greenwich, SE London ( GR8 ) PM 10, PM 2.5, NO X, O 3 Westhorne Avenue Greenwich, South East London ( GR9 ) North Circular (Ikea), Brent, North West London ( BT4 ) Blackwall Tunnel N. Approach, Tower Hamlets ( TH4 ) FDMS PM 10, FDMS PM 2.5, NO X, O 3, meteorology PM 10, PM 2.5, NO X, O 3, P NUM, CBLK, meteorology FDMS PM 10, FDMS PM 2.5, P NUM, CBLK, NO X, O 3, meteorology 5
Traffic data Automated Traffic Counters (ATC) covering all lanes adjacent to each supersite - Good coverage, but limited vehicle information - Four length classes approximating to Phases 1, 2 and 3 Automatic Number Plate Recognition Cameras (ANPR) covering one lane at closest available gantry - Detailed vehicle information but limited coverage - Euro class, compliance type, age, weight etc etc Assessed changes in fleet emission class profile and vehicle volume changes at each supersite 6
Feb-07 Jul-07 Feb-08 Jul-08 Mar-09 Aug-09 Feb-07 Jul-07 Feb-08 Jul-08 Mar-09 Aug-09 Feb-07 Jul-07 Feb-08 Jul-08 Mar-09 Aug-09 Proportion of fleet (ANPR data) Phase 1 & 2 compliance rates (TH4) Comply (Euro IV) Comply (Euro III) Non-Comply (from Feb 08) Non-Comply (from Jul 08) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% HGVs >12t HGVs 3.5t-12t Buses 7
Mean daily total - HGVs >12m Mean daily total - Cars & Taxis Vehicle flows following Phase 2 (BT4) 100000 90000 80000 70000 60000 Cars & Taxis 50000 40000 30000 20000 10000 PreMean PostMean 0 Sunday Monday Tuesday Wednesday Thursday Friday Saturday HGVs >12m 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 PreMean PostMean 0 Sunday Monday Tuesday Wednesday Thursday Friday Saturday 8
Mean daily total - Bus Lane Mean daily total - Cars & Taxis Vehicle flows following Phase 2 (MY1) 80000 70000 60000 50000 Cars & Taxis 40000 30000 20000 PreMean PostMean 10000 0 Sunday Monday Tuesday Wednesday Thursday Friday Saturday 1600 1400 1200 Buses 1000 800 600 400 PreMean Bus PostMean Bus PreMean Bendy-bus PostMean Bendy-bus 200 0 Sunday Monday Tuesday Wednesday Thursday Friday Saturday 9
Proportion of fleet (ANPR data, single lane only) Contrasts in fleet composition (2007) 100% 90% 9% 11% Taxis Cars LGVs & Minibuses Buses HGVs 6% 1% 80% 70% 60% 50% 40% 30% 20% 10% 0% BT4, Ikea TH4, Blackwall N Approach HK6, Old Street MY1, Marylebone Road Outer London Inner London Derived from single lane ANPR data extrapolated to all lanes using ATC data 10
Traffic data Each supersite has a different traffic profile The introduction of the LEZ did not significantly change vehicle flows or composition Emissions classes of affected vehicles changed rapidly - Compliance rates of articulated HGVs entering the zone increased from around 80% in 2007 to more than 98% by the second half of 2008. - The shift in 3.5t-12t HGVs was even greater (c. 75% to 97%). 11
Pollutant data In order to isolate change in pollutant concentrations caused by the LEZ itself analyses must account for: - The influence of meteorology - Regional sources of pollution - Changes in vehicle emissions not related to the LEZ (e.g., passenger vehicle numbers) - Local emissions from non-vehicle sources (industrial) Due to it s composite nature, PM 10 presents the greatest challenge! 12
13 Removal of regional sources - background control paired sites
Filtering of local vehicle emissions (BT4) BT4 local NO X N 160 BT4 local PM 10 N 25 10 5 5 140 20 120 W E 100 W E 15 80 60 10 40 5 S NO X S PM 10 NO X BT4 local PM 2.5 N PM 10 10 10 5 8 6 W E 4 PM 2.5 S 2 pm2v 14
Filtering of local vehicle emissions (MY1) MY1 local NO X N MY1 local PM 10 N 10 5 200 5 25 150 20 W E 100 W E 15 10 50 5 S NO X S PM 10 NO X MY1 local PM 2.5 N PM 10 10 16 5 14 12 10 W E 8 6 PM 2.5 S 4 2 PM2.5 15
Change in local filtered PM concs. 30 Filtered mean concentration / mg m -3 25 20 15 10 5 BC (*0.5) local PM10 local PM25 0 Year-2 Year-1 Year+1 Year+2 Year-2 Year-1 Year+1 Year+2 Year-2 Year-1 Year+1 Year+2 Year-2 Year-1 Year+1 Year+2 BT4 TH4 MY1 HK6 16
Change in local filtered NO X concs. 400 Filtered mean concentration / mg m -3 350 300 250 200 150 100 50 local NOX local NO2 0 Year-2 Year-1 Year+1 Year+2 Year-2 Year-1 Year+1 Year+2 Year-2 Year-1 Year+1 Year+2 Year-2 Year-1 Year+1 Year+2 BT4 TH4 MY1 HK6 17
How much of PM 10 is HGV tailpipe? Mass closure chemical speciation at TH4, winter 2008 c. 15% of total PM10 mass is Elemental Carbon 18
Summary 15% / 1 µg m -3 per year decrease in concentrations of black carbon and non-regional PM 2.5 at roadside locations. Change unclear in central London due to higher proportion of taxis and buses. No evidence of an LEZ-related impact on primary PM 10 found. Elemental carbon comprised of c. 15% of the total PM 10 mass, therefore exhaust emissions-based traffic controls such as the LEZ are unlikely to have a large effect on PM 10 mass. Identifiable impact on more harmful component of PM 10 Has the LEZ been successful? 19
Thank you benjamin.barratt@kcl.ac.uk