Highways Agency

2. The Highways Agency's Role

Our purpose is to operate, maintain and improve the strategic trunk road network with one of our objectives being to respect the environment. We can influence our effect on air quality through:

• contributing to strategic planning;
• road improvements;
• integrating transport and encouraging sustainable travel;
• providing better information for improved operation; and
• working with local authorities to deliver the Air Quality Strategy.

Our plans for the network are discussed below together with how these could affect air quality. Local authorities will need to be aware of these when assessing air quality and preparing their action plans.

2.1 Strategic Planning

2.1.1 Multi-Modal Studies

In the past, road congestion, safety and environmental problems have been addressed by simply increasing road capacity. There is still a need on occasions to look solely at road based solutions but the purpose of the multi modal studies is to examine the role of all transport modes in the area or corridor concerned to identify the contribution that each can make to solving the problems of the corridor and meeting the objectives for sustainable development.

The multi-modal studies do not look simply at a congested or unsafe stretch of road to decide what improvements could be made, but also examine what scope there may be for expanding public transport or for traffic management measures to manage the demand on the existing infrastructure. A strategic level assessment for air quality according to the Guidance on the Methodology for Multi-Modal Studies (GOMMMS) has generally been carried out as part of these studies for the proposed strategies and for the do-minimum scenario. This involves identifying the change in emissions of NOx and PM10 expected in each zone within the study area for each strategy and relating it to the population within that zone.

After reviewing the multi-modal studies, the Department for Transport makes recommendations as to which schemes should go-ahead. These recommendations are based on the Government's objectives for transport. Some schemes have been turned down on environmental grounds. If a scheme is approved, it will then enter the Targeted Programme of Improvements (see section 2.2.1) and will be subject to rigorous appraisal.

Information on the multi-modal studies is available from the Government Office for each region. The web addresses for each Government Office are given below:

South-east (http://www.go-se.gov.uk)
Eastern England (http://www.go-east.gov.uk)
East Midlands (http://www.goem.gov.uk/)
South West (http://www.gosw.gov.uk)
North West (http://www.gonw.gov.uk/)
North-east (http://www.go-ne.gov.uk)

The map below indicates the areas that have been addressed in the multi-modal studies.

2.1.2 Managing Demand

It is widely accepted that it will not be possible to build our way out of the increasing pressure on road space. The Department for Transport has published a discussion paper "Managing our Roads" to stimulate discussion around the key themes of tackling congestion and managing demand for road space. It considers how demand for road travel might increase into the future, what measures might be taken to reduce the need for car travel, how to make best use of the existing network and the choices to be made to balance the issues of capacity and demand. The document can be viewed at http://www.dft.gov.uk/stellent/groups/dft_transstrat/documents/page/dft_transstrat_022865.hcsp.

The Department for Transport has commissioned a feasibility study to look at the practicalities of road user charging to reduce demand. There are a number of issues that need to be addressed such as protection of privacy and whether any scheme could work technically. Road user charging was part of the strategy in some of the multi-modal studies.

2.1.3 Route Management Strategies

Route Management Strategies (RMS) are about making better use of the existing roads. The process has been developed to help the HA to focus on local needs, consider how to integrate roads planning with other transport and planning decisions in addition to looking at the regional picture. This is done by taking a strategic approach to the maintenance, operation and improvement of its network, and involving regional stakeholders and the public in the decision-making process. Each RMS will lead to the adoption of a ten-year strategy and a three-year investment plan for each of the routes comprising the strategic road network. It is the intention that every route in the strategic road network has a RMS in place by March 2004.

The main features of a RMS are:

• study of existing and likely future conditions including identification of AQMAs;
• involving key groups including road user organisations and local authorities from an early stage;
• closer involvement of these groups in the decision-making process should encourage partnerships to develop between various transport modes, encouraging a more unified approach to improving services;
• workshops and seminars, public exhibitions and roadshows; and
• publishing strategy and delivering improvements.

As an example of what can be done through RMS, the RMS for the M5 Junction 21-31 (Weston-Super-Mare to Exeter) recommended

• congestion near junctions should be reduced by increasing capacity through altering road markings and signal times,
• providing car parks near junctions to enable drivers to share cars thus reducing traffic flows,
• promoting alternative modes of travel through the travel industry during the holiday periods,
• using variable message signs to advise drivers when car parks at MSAs are full so avoiding queues backing onto the motorway,
• providing long distance coach stops at junctions with connecting local bus services
• travel demand management using ramp metering at selected junctions to prevent flow breakdown on the main carriageway

The RMS for the M26/M20/A20 in Kent identified improving air quality as one of 13 high priority actions. It will investigate solutions such as reducing congestion and will consider speed and access control.

The local authority will be notified via a press notice that the HA intends to develop a RMS in their area. Seminars and consultations will be held during the development of the Strategy to enable stakeholders and consultees to express their views. The local authorities should take an active part in the development of these RMS to ensure that appropriate strategies are developed that take account of local conditions and their concerns. If a road is identified as already being at capacity, the RMS would include a land-use planning and development control statement to restrict any development that would increase flows on that road.

2.2 Road Improvements

All of our schemes are subjected to the standard procedures for rigorous appraisal, including an assessment of their impact on air quality, and progression is dependent on the satisfactory completion of statutory procedures.

The air quality assessment would include, as a minimum, an assessment of the overall change in NO2 and PM10 concentrations at properties as described in the DMRB. The larger schemes would require Environmental Statements that would contain an air quality assessment carried out in accordance with the guidance in the DMRB. This would include:

• estimated pollutant concentrations at selected properties with and without the scheme and a comparison with the Air Quality Strategy objectives,
• an estimate of the overall change in NO2 and PM10 concentrations at properties due to the scheme, and
• an estimate of the change in regional emissions due to the scheme.

2.2.1 Targeted Programme of Improvements

The Targeted Programme of Improvements (TPI) aims to address some of the most pressing network problems, easing congestion and making travel safer, providing safer and healthier communities and supporting regeneration and integration. The schemes comprise of a number of major schemes each costing more than £5m, funded either conventionally or by public-private partnership.

When announced in 1998 as part of "A New Deal for Trunk Roads in England", the TPI consisted of 37 schemes. Since then further schemes have been added, some of which are due to the outcomes of the multi-modal studies. The schemes included in the programme are listed in Annex 1. Further information on each of these in terms of progress and the Appraisal Summary Table, which includes the expected effect on local air quality, is available at for all the TPI schemes. Local authorities should include these schemes in their review and assessments if they are expected to be operational during the assessment years.

Road Improvements

2.2.2 Junction Improvements

Ninety two junction improvement schemes will be carried out over the next five years to tackle congestion and improve safety at junctions across England's trunk roads and motorways. These schemes will address some major bottlenecks so cutting queues, improving traffic flows leading to more reliable journey times and reduced emissions. Locations where problems have been identified range from major motorway junctions such as junction 10 on the M62 near Warrington, to congested dual-carriageway roundabouts such as the A38 at Derby, to crossroads such as on the A64 at Bramham in Yorkshire.

2.2.3 Local Network Management Schemes

These are small schemes aimed at making better use of the network as it stands. Whilst many of them relate to improving safety, they can also deliver improvements to air quality.

2.3 Integrated Transport and Sustainable Travel

2.3.1 Encouraging Travel Changes

By widening the choice of transport available for the movement of people and goods, rather than relying solely on roads, levels of congestion and pollution could be reduced. The Agency can play its part by helping to develop proposals for passenger and freight interchanges, offering better information about travel choices, and giving priority at specific locations to particular classes of vehicle. Our objective is to work with others to ensure passengers and freight operators can switch efficiently and smoothly between different modes of transport, and to broaden the choices available. It is also important to ensure that our activities reflect Government policy across the whole spectrum to promote safe, healthy and inclusive communities.

Our role is described in more detail.

Actions we can take include:

• Developing solutions to facilitate the provision of interchanges between road and public transport, walking or cycling.
• Identifying ways we can assist bus and coach operation, and promote car sharing on and around the network, through designated lanes and priority measures.
• Investigating ways to improve freight operations on the network, including consideration of designated lanes and the potential for freight interchange facilities and transhipment depots.
• Working with port and airport operators to further encourage access by bus and rail.
• Working with waterway operators and associated organisations to further encourage sustainable transport.
• Increasing the quality and availability of travel information in order to enable informed choices to be made.
• Setting an example by encouraging greater use of technology within the Agency to reduce the need to travel.
• Continuing to review design standards to ensure that the needs of all users are reflected.
• Supporting the development of school travel initiatives
• Promoting healthy lifestyles, by encouraging walking and cycling.

Examples of where we have done this include:

• Facilitating the development of Hams Hall rail freight terminal near Birmingham by improving the trunk road network.
• Working closely with Bedfordshire County Council in the development of school travel initiatives including the provision of publicity material and improved facilities for cyclists and pedestrians.
• A partnering agreement with Stoke-on-Trent City Council to develop a £24m project to improve the town centre and surrounding area. This joined up approach to integration will ensure our road proposals are in-line with Stoke's transport proposals.
• Erecting signs on the southbound carriageway of the M1 at Luton to direct drivers to the new parking facilities at Luton Airport Parkway Station which provides a convenient rail alternative for journeys to London. This was undertaken in conjunction with Thameslink and Luton Borough Council.

We have also carried out pilot studies with local authorities and transport operators to develop campaigns to encourage a switch from road to rail. Three campaigns were held to explore the difficulties and benefits of different transport organisations working together.

The A12 Chelmsford to London is an important commuter route where the main rail route to Ipswich closely parallels the trunk road. The campaign, run in partnership with First Great eastern, encouraged a switch to rail at peak times. Six percent of people who recalled receiving the publicity leaflet said that they had changed their travel behaviour as a result. Eleven percent of these caught the train instead of driving with the remainder not driving to the station or making fewer journeys.

The A47 from Norwich to Yarmouth is a route which has the potential to switch both leisure and commuter trips to the parallel rail and high quality bus routes using special ticketing offers promoted by the operators Anglia Railways and First Eastern National. A "kids travel free" offer attracted over 500 users and "two weeks for the price of one" 50 users. The savings from the special offer were the prime motive for the change in behaviour with 20% of those travelling having changed their mode of travel as a result.

The A696/A1 north-west Tyneside to Newcastle is an urban corridor with potential to increase park and ride at two stations on the existing metro. The campaign was conducted in partnership with Nexus and provided a free service. The park and ride utilisation increased significantly during the campaign period and the increase was maintained afterwards.

Further information on these pilot studies.

2.3.2 Encouraging Sustainable Travel

As operator of the nation's strategic roads, we have a responsibility to all of our road users. Whilst most of the business is concerned with providing for the movement of motor vehicles throughout the network, there are also a significant numbers of non-motorised users whose needs must be addressed. These include pedestrians, cyclists and horse riders. Moreover, there is an important role to play in improving access to everyday facilities for those without access to a car - one of the Government's key transport objectives. We must also ensure that the needs of disabled people are met and that, as far as possible, we act both to reduce the severance effect which strategic roads can have on the communities through which they pass, and to improve access to public transport. A Strategic Plan for Accessibility has been prepared that explains how we intend to meet these challenges in the years ahead. However, implementing these plans requires partnership with other organisations.

Actions include:

• Working with public transport operators and local authorities to address access to bus and rail services on foot and by cycle and to improve facilities at bus stops.
• Working in partnership with local authorities in drawing up walking and cycling strategies.
• Working with Sustrans to assist in the completion of the National Cycle Network.
• Working with schools, local authorities, employers and other bodies to develop and implement school and workplace travel plans.
• Working with local authorities and other groups to improve conditions in bypassed towns.
• Continuing the introduction of traffic calming schemes in villages.
• Investigating the effects of vehicle speed, and introducing speed-reducing and speed- controlling measures where appropriate.
• Developing innovative measures to enable pedestrians, cyclists and equestrians to cross busy trunk roads with improved safety and personal security.
• Working to ensure good access arrangements for pedestrians and cyclists in and around developments near trunk roads.
• Ensuring that maintenance of footways, cycle tracks and crossings is carried out regularly and using maintenance schemes to provide enhanced facilities.
• Where possible, working with other bodies to provide more direct routes for walking and cycling between key destinations.
• Upgrading existing facilities as new ideas are introduced.
• Working with public transport operators and local authorities to ensure that infrastructure improvements are implemented in tandem with service fleet changes (such as low-floor buses).

Examples of where we have done this include:

• Constructing the missing link in a six mile cycle route along the A46 northbound embankment between Lincoln and the Nottinghamshire village of Harby to create the Skellingthorpe Cycleway, part of Route 64 on the Sustrans National Cycle Network, which runs from Newark to Lincoln. It incorporates a series of ramps to take cyclists down a steep embankment safely.
• Constructing a joint cyclepath and footway next to the A66 in Penrith to encourage local pedestrians and cyclists back onto the key route.
• Implementing environmental improvements including traffic calming and bus lanes on the A5 at Dunstable.
• Building bridges to cross busy roads such as the M1.

2.4 Better Information and Improved Operation through Technology

2.4.1 Real-Time Traffic Information

In order to avoid congestion, travellers can currently obtain real-time information on traffic speeds for a number of areas on the motorway network (M25, Kent, Birmingham, Leeds and Manchester) and can then plan their trip accordingly. In addition, the TrafficMap service provides comprehensive information about motorway incidents and what the motorway signs are saying to help plan the journey.

The traffic control centre (TCC), due to open in 2004, will introduce coordinated up-to-the-minute information on the majority of the strategic road network. The information will be available to travellers and organisations such as the police, local highway authorities and other transport operators. The TCC will focus on journeys made on the nationally important parts of the strategic road network. It is planned that the information gathered will be integrated with information collected from other Government initiatives looking at other transport modes (e.g., train, bus, air).

By providing the right information where and when it is needed, the TCC aims to:

• Improve journey time reliability;
• Reduce disruption caused by major incidents;
• Provide alternative route advice to minimise the effect of congestion and incidents
• Minimise delays due to roadworks; and
• Influence road users' decisions before they set out on a journey about route, time and means of travel.

2.4.2 Active Traffic Management

The aim of Active Traffic Management is to contribute towards easing congestion, safer travel, better information and smarter roads. Easing congestion should lead to an improvement in air quality for some pollutants.

The benefits provided to the road user will be:

• Reduced congestion through more efficient use of road space;
• Faster response to incidents and reduced clear-up times;
• Enhanced driver information;
• More reliable journey times; and
• Reduced driver stress.

Where appropriate, ATM will incorporate the following features:

• Lightweight gantries with lane specific signals and signs, variable speed limits, digital enforcement equipment and variable message signs;
• High tech information systems, CCTV cameras and automatic queue detection (MIDAS - Motorway Incident Detection Automatic Signalling) to monitor traffic conditions;
• Rapid incident response teams to remove obstructions, assist with traffic management and repair roadside equipment;
• Ramp metering (this involves traffic signals on the slip roads immediately adjacent to the main carriageway enabling a smoothing effect on the traffic joining the motorway);
• Lane marshalling by destination and/or vehicle type; and
• Controlled use of the Hard shoulder as an additional running lane.

ATM is being piloted on the M42 Junction 3A-7 which is the south-eastern quadrant of the M42 around Birmingham. The impact on air quality will be assessed during the pilot study which will commence in 2003.

2.4.3 Message Signs

If drivers are made aware of the location of AQMAs, then they may be willing to modify their activities to reduce emissions. To this end, we are liaising with the DfT and Defra to design a road sign that could be used nationally to advise drivers that they are entering an AQMA. Static signs could also be erected to advise of Park and Ride or other similar facilities in support of initiatives being carried out by local authorities, provided that those facilities meet certain standards.

Variable Message Signs could also be used to advise of poor air quality and encourage drivers to modify their activities. Again, we are liasing with Dft and Defra to identify appropriate messages. Clearly, these messages could only be deployed on routes equipped with Variable Message Signs.

We will be preparing a paper in association with DfT, Defra and the local authorities on the signing strategy.

2.4.4 Traffic Management during High Pollution Episodes

As part of the DfT's TRAMAQ research programme, an assessment was made of the feasibility of using traffic management measures during high pollution episodes to improve air quality (UG212). High pollution episodes tend to be caused by specific meteorological conditions rather than increased emissions and are an infrequent event. The measures considered were wide-area access control, parking charging / restriction, influencing key traffic generators, voluntary restraint and urban traffic control systems. Forecasts of these events would need to be given 1 to 3 days before the event to enable people to modify their normal travel patterns. It was considered that there was relatively good infrastructure already in place for the dissemination of this information to the public. However, the costs involved in undertaking high pollution traffic management were considered to be substantial because of the temporal, geographical and institutional extent of the activities that are likely to be involved. Some improvements in air quality were likely to be achieved with the most restrictive measures but the effort and costs involved were considered likely to outweigh the benefits. The report concluded that it would be better to have on-going long-term traffic management measures.

2.5 Working with Local Authorities to Deliver the Air Quality Strategy Objectives

We have a direct involvement with the review and assessment process in a variety of ways. These include providing the DMRB air quality screening method to estimate concentrations near roads, providing traffic data, monitoring pollutant concentrations, reviewing the local authority's reports and participating in action plan meetings which will lead to implementing measures to improve air quality.

2.5.1 DMRB Screening Method

We have recently updated the DMRB screening method to take account of revised vehicle emission rates, revised fleet composition data, changes to the Air Quality Strategy objectives and to improve the accuracy of the method. The performance of the method has been assessed by comparing estimated concentrations with measured values at DEFRA's AURN and our monitoring sites. The comparison can be seen at http://www.trl.co.uk/ (select calibration report). This revised screening method is the cornerstone of road assessments in the second phase of review and assessment.

2.5.2 Monitoring Concentrations

We currently monitor air pollution concentrations at four kerbside sites on our network - M60 Manchester, M25 Staines, M4 Theale and A40 Cheltenham. Details of the sites and the measured concentrations are hosted at http://www.trl.co.uk/. We also measure pollutant concentrations in the vicinity of a number of our larger schemes. This data is also available to the local authorities upon request, to assist with the review and assessment process. The local authority should liaise with the HA Project Sponsor for the scheme as to whether any monitoring is being carried out in the area. Modelled concentrations are also likely to be available for the scheme for a base year and an opening year both with and without the scheme.

2.5.3 Traffic Data

Traffic flows are routinely measured across the strategic road network using automatic traffic counters. There are two types of counter, a single loop that measures traffic flow only and a double loop that measures traffic flow and the number of heavy duty vehicles (> 5.2 m). These counters are 95% accurate. The data is regularly reviewed to identify any gaps or unusual results. Unusual results could be caused by a faulty counter or an incident on the local network. Erroneous data is removed and any gaps filled in. This data then forms the modified dataset. The data of most interest for review and assessment will be the annual average daily traffic (AADT) flows and annual average hourly flows throughout the day.

Traffic flows in future years can be estimated by applying growth factors to the measured flow data. Table 3 in the National Road Traffic Forecasts (Great Britain) 1997 provides forecasts of national growth for motorways, trunk roads and other roads in urban and rural areas . The forecasts are given as distance travelled relative to that in 1996, for 2001 and then every ten years. The annual average percentage increase (expressed as a factor) for each type of road is shown in Table 1 below. These factors should be used to estimate the growth between the year with measured traffic data and the year of interest.

Source: National Road Traffic Forecasts (Great Britain) 1997

Note: Urban areas are those of continuous built development, while all others are rural. The resulting traffic figures differ from the published traffic statistics presented on the build-up and non-build-up basis, which are solely determined by speed limits. Thus roads in urban areas with 50mph and higher speed limits are urban for the purpose of these forecasts, but non-built-up for traffic statistics.

• ¹ Dual carriagway "A" roads
• ² Single carriagway "A" roads, B, C and unclassified roads
• ³ Dual and single carriagway "A" roads
• ⁴ B, C and unclassified roads

For example, suppose measured traffic flows on a rural motorway were 100,000 AADT in 2000 and flows were needed for 2005 and 2010. The calculation would be:

2005 flow = 100,000 x (1.0301) 1 x (1.0274) 4 = 114,772

2010 flow = 100,000 x (1.0301) 1 x (1.0274) 9 = 131,382

Alternatively, if it is likely that using national traffic growth factors would not be representative of local conditions, then growth factors from TEMpro could be used. These can be obtained from http://www.tempro.org.uk/

Traffic speed is not routinely measured at the moment but a limited amount of data is available. If no local data is available, speed can be estimated from the speed-flow graphs given in DMRB Volume 13, Section 1, Part 5, Chapter 9. This can be viewed at http://www.standardsforhighways.co.uk/dmrb/index.htm

Traffic flows and speeds are held by consultants on our behalf. In due course, it will become available on the internet. In the meantime, it can be obtained from:

Southern Region (HA areas 1-5)
Richard Smith
Babtie
School Green
Shinfield
Reading
Berkshire
RG2 9HL
Tel: 0118 988 1608
Fax: 0118 988 1696
Email: hatraffic@babtie.com

Midlands Region (HA areas 6-9 and 11)
John Morris
Atkins Transport Planning
The Axis
10 Holliday Street
Birmingham
B1 1TF
Tel: 0121 483 5414
Fax: 0121 483 6161
E-mail: john.morris@atkinsglobal.com

Northern Region (HA areas 10, 12-14)
Martin Morson
WSP Transportation
6 South Park Way
Wakefield 41 Business Park
Wakefield
West Yorkshire
Tel: 01924 206628
Fax: 01924 368468
Email: martin.morson@wspgroup.com

2.5.4 Liaison with Local Authorities

By March 2003, 115 local authorities in England had declared Air Quality Management Areas. Just over half of these include HA roads. The AQMAs that include strategic roads are shown in Annex 2. Many of these are located near major conurbations such as the M25 near London, M60/M62/M66/M61 near Manchester, M4/M5 near Bristol, M5/M42 near Birmingham and various sections of the M1 in urban areas. Some of the AQMAs are near rural motorways where there are just a few dwellings close to the road whilst others cover entire boroughs. The size and number of AQMAs is subject to change as local authorities collect more monitoring data, revise traffic data and revisit the modelling as part of DEFRA's rolling programme for review and assessment. Some of the AQMAs declared for HA roads have been revoked as the monitoring data collected showed that measured concentrations were lower than those modelled, and it is likely that other revocations will follow.

Local authorities are required to consult with us if their review and assessment includes a strategic road. They should contact the route manager in the first instance. In the unlikely event that this proves to be unproductive, then Michele Hackman in the Environmental Policy team should be advised of the situation (Michele.Hackman@highways.gsi.gov.uk) Upon receiving a report, we will review it and pass our comments to the local authority. We will be particularly looking at the model result verification, the results from monitoring and the distance between the properties and the road. The number of properties affected and the highest predicted concentrations will also be of interest.

Once the AQMA has been declared, the local authority should invite the route manager to discuss how we can assist with improving air quality. A list of traffic management measures that could be considered is given in Annex 3. In delivering individual local measures to contribute to improved air quality, we must take into account the Government's five core policy objectives (environment, safety, economy, accessibility and integration) and assess how the proposed measure performs against these objectives. Further information on this is available in the Guidance on Methodology for Multi-Modal Studies. There must be a robust case for the mitigation measure for it to be considered further.

The action plan prepared by the local authority could include a suite of proposals to target the various causes of the emissions, for example, roadside emissions testing to reduce emissions from high emitting vehicles, workplace and school travel plans to reduce traffic flows, new developments to be served by public transport and accessible by non-motorised users to reduce additional demand, promotion and improvement of public transport to reduce traffic flows and junction improvements to reduce congestion.

Speed limit reductions are sometimes suggested as being a "quick-fix". Whilst in theory a significant speed reduction would deliver decreased emissions, in practice there are confounding factors and potential issues which need to be considered: roads are becoming increasingly congested so the benefits would be less than expected (please see section 3.1) with benefits decreasing in future years, a reduction in speed could increase capacity, this could lead to increased traffic flows, and most importantly, the speed limit would need to be enforced to ensure compliance which has high costs. As part of understanding these issues more thoroughly, we are assessing the possibility of a speed reduction on the M1 as part of our involvement in Sheffield's action plan.

The route manager should be able to comment on whether the proposals suggested by the local authority for strategic roads are feasible for the area concerned, whether any of our other projects may have an effect and whether further work should be carried out to assess the proposed mitigation measures in more detail. The local authorities should seek confirmation from the route manager that we are in agreement, subject to any further studies needed, with the measures proposed for the HA to implement.

2.5.5 The HA's Performance Targets

One of the Agency's key objectives is to respect the environment. A key performance target is set each year for air quality. In previous years this has been to respond to 95% of review and assessment consultations. In the current year it is to improve air quality in four AQMAS. We are currently considering a revised performance measurement for local air quality to better reflect the impact of the HA's activities.

In addition to the Agency's own performance targets for air quality, there is a Public Service Agreement (PSA) target that is jointly owned by the DfT and DEFRA. The target is "to improve air quality by meeting the Air Quality strategy targets for carbon monoxide, lead, nitrogen dioxide, particles, sulphur dioxide, benzene and 1,3-butadiene".