Open Geocomputation: CO2 Emissions and the Pupil School Commute

RGS Conference 2013 - 29th August, London.

Transcript

1. Alex Singleton Department of Geography and Planning ! www.alex-singleton.com Open Geocomputation: CO2 Emissions and the Pupil School Commute http://www.flickr.com/photos/epsos/5591761716/sizes/o/in/ photostream/
2. Overview • Rates of active transport (e.g. cycling or walking) to school are in decline • Pupil-school commute is estimated to contribute around 658k tonnes of CO2 / year • Transport adopted for the pupil-school commute has obvious implications for CO2 emissions
3. Traditional Estimation Technique • Euclidean Distance • Euclidean distance • Average emissions values for mode of transport 183.2 vehicle CO2 g/km (DEFRA 2011) ! SL – trip – 1.2km ! 1.2 * 183.2 = 219.84 CO2 g / journey ! Daily commute - 219.84 * 2 = 439.68 OpenStreetMap
4. Problems • No account for real world geography – Straight lines will typically underestimate true distances • No sensitivity to different vehicle types – What about train / bus etc? • Geocomputation provides a solution…
5. Challenges • Estimate transport network level routes for pupil journeys • Account for variable CO2 emissions between different vehicle types • Individual level for a national population?
6. Model • d distance • p pupil • i pupil home postcode • j school postcode • e CO2 g/km • t transport mode • g location k p = 2 d i p j p t p ( )e t p g p ( )w t p ( ) ( ) Distance CO2g/km Weight
7. Pupil Data • Department for Education – Pupil Level Annual School Census (PLASC) • Postcode level • 2007 – 2012 – “usual” travel mode • 7,373,505 pupil records after exclusions (e.g. no postcode etc) – multiple years (2011) • Mostly state school pupils
8. Vehicle Data • Department for Transport – LSOA average CO 2 g/km for those vehicles registered within these zones – Driver Vehicle Licensing Agency (DVLA) • European legislation directive 91/441/EC – Cars registered after March 2001 • Caveat – Possible underestimation? » 162.9 CO 2 g/km differs from the DEFRA national estimate of 183.2 CO 2 g/km (DEFRA 2011). » Might be specific car types for school run?
10. Other CO2 g/km Values (Coley 2002, DEFRA 2011, Tranter 2012)
11. Data Processing OpenStreetMap railway=light_rail railway=subway PostGIS Road / Path Light Rail / Tube Routino .osm XML files Meridian2 Railway Lots of Cleaning! 1) Single lines 2) Nodes join 3) Nodes at stations Postcode Directory
12. Software Infrastructure PostGIS PgRouting Iterative process for each pupil Routino 1) Query pupil (origin, destination, mode) Rail / Light Rail 2) Mode Choice? Road Pupil (distance, mode) 3) Car based? Yes Return LSOA Avg. CO2 g/km No Use type averages Pupil (distance, mode, CO2 g/km) 4) Implement the model
13. Distance and Mode Choice
14. 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 0.00 0.25 0.50 0.75 1 2 3 4 5 6 7 8 9 10 11 12 13 0−0.5km 0.5−1km 1−1.5km 1.5−2km 2−2.5km 2.5−3km 3−3.5km 3.5−4km 4−4.5km 4.5−5km 5−5.5km 5.5−6km 6−6.5km 6.5−7km 7−7.5km 7.5−8km 8−8.5km 8.5−9km 9−9.5km 9.5−10km Distance Percentage Mode BUS CAR NON School Year • Over time increase in distance of non • Year 6-7 – large jump in distance non – Bus more prevalent
15. Model Output • Versus a simple model (straight line, vehicle national averages)
19. Next Steps • Estimating Bus Routes – Walk to bus stop – route to school? • Multimodal journeys • Data issues – E.g. confusion in London (tube, rail, light rail) • Scaling issues – This all takes a very long time! • Temporal changes – Policy evaluation
20. Any Questions?