Assessment of measures to improve air quality in Leiden

The Dutch Air Quality Decree requires all municipalities to submit an annual report on local air quality to the national government. In Leiden, the 2004 report indicated that the European standards for nitrogen dioxide (NOx) and/or particulates (PM10) levels had been exceeded at a number of locations that year.

Even without additional measures, the number of pollution ‘hotpots’ will have declined by 2010. This is because background concentrations will by then have fallen as a result of both European and national measures. During the derogation period (probably 2010 for PM10 and 2015 for NOx), however, the Netherlands will still have to meet European air quality standards across the country. In practical terms, this means that by this date the country must have effectively resolved all instances of air quality standards exceedance. This will require additional policy measures.

Having already taken a range of steps, Leiden municipality, by way of its Air Quality Taskforce (TL2), therefore asked CE to advise them on a number of additional measures from the local Air Quality Plan, as follows:

City-wide measures
1. Establishment of a ‘green zone’ for freight traffic, combined with alternative distribution concepts.
2. Use of ‘Site Transport Performance’ certification in (re)development projects.
3. Parking tariffs indexed to vehicle environmental performance.
‘Lead-by-example’ measures
4. A clean and fuel-efficient municipal vehicle fleet.
Site-specific measures
5. Synchronisation of traffic lights (‘green wave’) on certain local roads.
6. As 5, but for heavy goods vehicles only.
7. Introduction of LARGAS philosophy (Dutch acronym for ‘Driving slower gets you there quicker’) on certain local roads.
8. A split-level interchange on Plesmanlaan.
9. Wet-sweeping of local roads. *
(* This measure is not included in the Air Quality Plan, but was later added by TL2).

These additional measures were assessed by CE with respect to the following criteria: practical feasibility, impact on air quality hotspots in 2010, side-effects, costs, legal feasibility, lead time and public support. This assessment was based on a desk study, talks with experts from Leiden municipality and elsewhere, modelling simulations (CAR) and validation of interim results with a broad array of civic actors from the city.