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Mitigation Options for Motorways

Mitigation Options for Motorways. A review of the literature Roger Barrowcliffe and Michael Bull. Content. Context Defining the problem Sources of information Source – pathway – receptor Conclusions. Context. Pressure to enhance motorway network by increasing capacity

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Mitigation Options for Motorways

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  1. Mitigation Options for Motorways A review of the literature Roger Barrowcliffe and Michael Bull

  2. Content Context Defining the problem Sources of information Source – pathway – receptor Conclusions

  3. Context Pressure to enhance motorway network by increasing capacity Some schemes are unable to proceed because of their implications for air quality and compliance with limit values, chiefly NO2. In the absence of any control over the vehicle types using the motorway, what are the alternative means of reducing air quality impacts?

  4. Defining the problem M25, Essex 70 mph speed cars, 60 mph HGVs 2013 EFT 100.000 veh/day Clear Air Thinking

  5. Looking Ahead

  6. What we did Clear Air Thinking Consult with: Government departments, local government, government agencies, academics and European research organisations. Search scientific and grey literature, egthe Dutch InnovatieprogrammaLuchtwaliteitor IPL Analyse and evaluate findings Produce a draft report

  7. Receptors Clear Air Thinking Purchase properties? Not viable for a number of legal and ethical reasons Modify properties? eg forced ventilation. Technically dubious and legally suspect. See planning inquiry decision on student accommodation near Blackwall Tunnel.) Conclusion: little or no scope to solve problem by intervention at receptors.

  8. Pathway Clear Air Thinking • Pathway modifications through: • Barriers • Enclosure in tunnels • Pollutant removal by catalytic surfaces

  9. Barriers – the theory Clear Air Thinking

  10. Barriers – CFD modelling Barrier No barrier Notes: US EPA research Bowkeret al 2007 Birds eye view of a section of Interstate -440 in Raleigh, N Carolina Complements field study QUIC CFD model Clear Air Thinking

  11. Barriers – road layout for this US EPA study Clear Air Thinking

  12. Barriers – influence of buildings and trees Observation: The influence of obstacles behind the barrier dilutes its beneficial effect, in respect of pollutant concentrations Clear Air Thinking

  13. Barriers – experimental data Data from Dutch IPL Field experiments at A28 site Measurements made of NOx, NO2 and PM10 over several months 4m and 7 m noise barriers Clear Air Thinking

  14. Barriers - A28 results for NOx Clear Air Thinking

  15. Barriers – A28 result for NO2 Clear Air Thinking

  16. Pollutant removal Clear Air Thinking Catalytic surfaces using TiO2 for promoting oxidation to soluble nitrate. Theoretical – no practical experimental evidence to support this technique in real world conditions. Trials by HA alongside the M60 and also as part of the Dutch IPL. Fails because of insufficient surface area, insufficient UV light, damp surfaces and insufficient pollutant contact with coated surface. 1% reduction at best.

  17. Enclosures Clear Air Thinking

  18. Enclosures -feasibility Clear Air Thinking A largely theoretical concept Investigated as part of the Dutch IPL Would almost eliminate motorway as a pollution source along its length – although would concentrate pollution at tunnel portals. Dutch IPL quotes costs of €6M -€65M per kilometre Passive pollutant removal possible through catalytic coatings or pollutants dispersed as an elevated source through roof vents.

  19. The Melbourne ‘Sound Tube’ Real world example built as a noise barrier Melbourne CityLink urban freeway 300m long and costing AU$ 5 M No reported data on air quality implications Clear Air Thinking

  20. Emissions – speed reduction Clear Air Thinking • Influences on emissions: • Traffic volumes • Traffic composition, eg %age Euro VI/6 vehicles • Flow state, ie free flow or congested

  21. Speed limit reduction – the evidence Clear Air Thinking The most directly useful experience is that of Dutch urban motorways in the period 2002-2009. 80 kph speed limits imposed on 10 sections of motorway. Previous limits either 100 or 120 kph. Extensive roadside measurements made of air pollutants, especially in Amsterdam. Coupled with dynamic emission simulation modelling (VISSIM).

  22. Speed limit trial results (Kalteret al 2005) Clear Air Thinking

  23. The Dutch experience with speed limits – lessons learnt Clear Air Thinking The contribution of HGVs is important and influential in the outcome. Positive outcomes arise through smoothing of flows. Biggest improvements arise in PM concentrations, not NO2. This intervention is politically charged and polarising.

  24. Closing thoughts No easy solutions, but the HA is still committed to exploring options. Effectiveness of the obvious interventions is limited – except for theoretical and expensive solutions such as enclosures or canopies. Reducing emissions at source is ultimately the best solution – and will occur in time with the penetration of EuroVI/6 vehicles and the uptake of ultra low emission vehicles.

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