Bern: Air quality management and traffic policy

Abstract:

The City of Bern and Bern Canton have adopted a traffic management that aims to reduce emissions from motor vehicles on main streets by about 15-25 per cent. The planning for air quality should consider the needs of all traffic participants without designing new road capacity. The transportation policy can be regarded as an example of good practice for the following reasons:

• implementation of a steady traffic flow;
• combination of all transport modes and a correspondingly suitable street design;
• orientation towards a supply-orientated transport planning.

Concept and aims

The implementation of these framework conditions makes a new traffic planning philosophy necessary. The problems can not be solved with the traditional demand-orientated traffic models, which were aiming to adapt street capacities to the expected demand of mobility. What is necessary is supply-orientated transport planning to show how mobility needs might be fulfilled despite reduced road capacities, in which public transport, private vehicle traffic and non-motorised traffic can be combined. Supply-orientated transport planning is an important necessity to comply with environmental regulations. Defined provision of rail and street network helps to reduce traffic in general and therefore also the emissions which are this caused. On the local level supply-orientated transport planning is the prerequisite for steady traffic flow.

1. Supply-orientated transport planning

Primary new mobility habits are necessary to reach a reduction of private vehicle traffic. Supply- orientated transport planning is based on the knowledge that people adapt their individual mobility habits to the given circumstances. It is impossible to promote public transport without attendant measures in the road network. The focal point of planning measures is to be found in the infrastructure sphere. Supply-orientated transport and road planning has different tasks: firstly there has to be a adequate provision of traffic infrastructure in the future and secondly the quality of life in urban areas is to be improved, and the limit values for air and noise pollution are to be observed. Thirdly it has to be assured that latitudes are open if necessary for future settlement and economic developments.

2. Steady traffic flow

An important part of traffic emissions is caused by acceleration. Todaytraffic flow on highly frequented streets in residential areas is characterised by decelerations and accelerations. These manoeuvres result from the different claims of all road users to the street space. Emissions can be reduced with design and operational measures, which lead to a homogenised traffic flow. What must be obtained is a driving behaviour according to the following three criteria:

• a slow ascent of the acceleration after decelerations and stops
• a minimal speed fluctuation between terminal speed and journey speed
• limitation of traffic hold-ups

Steady traffic flow is only to be achieved if the traffic network is not overloaded. The principle that is applicable is that a road should be operated at no more than 80 per cent of the maximum capacity if a steady traffic flow and an emission reduction is to be reached. So measures which should effect a traffic steadiness should always include traffic reduction. In addition to the local measures operation- and design concepts are necessary. The road sections must be designed so that the different claims of all road users can be fulfilled and also that a constant traffic flow can take place. Possible measures are controlled or uncontrolled junctions, priority junctions, junctions with signals and roundabouts. On the links there are as constructinal measures turning lanes, central islands, central multiple- purpose lanes, cycle lanes and bus tracks,bus bays and -stops and speed reductions possible.

The compatibility standards between settlement, environment and traffic are measured by different criteria. In order to consider the different situations the traffic network has to be categorised into sections, which describe the various surrounding scenarios and regard the resulting requirements as to their compatibility (e.g. streets through residential areas or the roadside use is less sensitive to immissions). The assessment of the loading capacity is based on the following criteria:

• Noise and air pollution
• Steady traffic flow
• Technical serviceability of the road system
• Separation effects of roads and crossability
• Bus and tram traffic
• Design quality of the street space

Measures to increase the loading capacities of streets (e.g. construction of centre islands to improve crossability) as well as measures to reduce the loading capacity (e.g. street surface renewal to lower noise pollution) have to be included.

Implementation

In several streets observations and measurements were made. Foremost strongly loaded streets in densely built resident areas were observed. Apart from the motorways these streets cause the main part of the pollution by traffic. The evaluation and analysis of this inquiry showed, that from environmental motives one can basically distinguish between four types of transverse profile:

• Narrow streets without possibility of changing the land use
  Type A1: with few incidents and cross overs

  Type A2: with many incidents

• Broad streets with possibilities to change the land use
  Type B1: with few incidents and cross overs

  Type B2: with many incidents

According to the environmental effects the specific local handling with these four types of transverse profile a decisive key to smooth the traffic flow as well as to reduce the environmental burden. The types of transverse profile do not replace the instruments of street design, they represent the basis of their efficient use.

Narrow streets types A1 and A2

Narrow streeets with a lot of traffic produce always the impression of a latent risk of accidents. This impression leads to a raised attention of all traffic users. As long as the traffic is not handicapped by too many incidents a harmonious traffic flow on a low speed level (35-40 km/h) can develop. Because of the high attention of all traffic users these types of transverse profile can to be managed by experienced bikers and pedestrians. For less experienced cyclists and pedestrians the conditions are more difficult.

Type A1: As a result of the increased attention a steady traffic flow can be determined. From the environment political point of view this can be judged positive. For reasons of the steady traffic flow there does not exist any redevelopment needs. In many cases improvements for cyclists and pedestrians are necessary.

Type A2: Frequent turnings and numerous cross overs of pedestrians and bikers lead to congestions and incidents of the traffic flow. If measures should be taken against this it should also be considered that narrow streets, which could be judged as environment political positive, should not be disturbed in their character.

Broad streets types B1 and B2

These streets seem to be orderly and less dangerous than narrow streets. The relative traffic speed is noticeably higher so that pedestrians and bikers use the road space under more difficult conditions. Especially weaker road users need more time to cross over.

Type B1: If the street is located in an area with little turning and crossing needs from the environmental point of view there is no need for a redevelopment concept.

Type B2: Broad streets with frequent turning and crossing needs cause more environmental impact than narrow streets. The reason is primarily the higher traffic speed, which leads in the case of incidents more often to stops and accelerations. A redevelopment need often exists because of a steady driving behaviour.

Redevelopment concepts

The redevelopment concepts need to be locally differentiated:

• In suburb areas with little crossing and turning needs e.g. circle islands and turning bays for single cars can help to reduce upsets of the traffic flow to a few vehicles
• In centres with frequent pedestrian crossings multiple purpose lanes in the middle of the street are more suitable. They allow bikers and pedestrians to align their crossings wizh breaks in the traffic flow. So impacts can be reduced in this way.
• If there are no possibilities for structural redevelopments e. g. separated areas for bikers and pedestrians then the compatibility between motorised and non-motorised traffic can be achieved by speed limits of 30 km per hour
• In most of the cases roundabouts guarantee a steady traffic flow at junctions
• In special cases e.g. pre-emption of the public transport, vehicle- actuated traffic controls are suitable

Results and Impacts

General saving potential of throughroads (Bernstrasse/Zollikofen project)

In Bernstrasse in Zollikofen the two most important junctions were replaced by roundabouts. By dividing the carriageway in the centre and the creating of centre islands, times for crossovers could be shortened and crossings could be made possible on the whole link. Altogether there were little conflicts to resolve with the public transport. It will be assumed that the number of crossings and turnings will not change but that stops will be replaced by deceleration. The general saving potential for fuel consumption and emissions is 15-25 per cent compared with the undeveloped condition.

Advantages of roundabouts (Bärenkreuzung/Zollikofen project)

In comparison with the earlier light signal the roundabout leads to the saving of fuel and emissions by about 17 per cent.

Effects of steady driving behaviour (project Bernstrasse/Zollikofen)

If events like pedestrians crossing or vehicle turnings disturb the traffic flow for less than five seconds stops can be avoided. Instead of stopping the drivers react with a deceleration of 20-30 km per hour.

Finance

Financial survey concerning measures in the Bernstrasse/Zollikofen according to the civil engineering authority (Tiefbauamt) of the canton Bern, 9 January, 1995 (in million SF)

Source of Information

Bau-, Verkehrs- und Energiedirektion des Kantons Bern, Tiefbauamt (Hrsg.) 1995: Luftreinhaltung und Verkehr, Angebotsorientierte Verkehrsplanung als Beitrag zum Vollzug des Umweltschutzgesetzes, Praktische Wegleitung für Straßenplanung und Straßenbau, Bern

Bau-, Verkehrs- und Energiedirektion des Kantons Bern, Tiefbauamt (Hrsg.) 1995: Grundlagen zur Wegleitung für Straßenplanung und Straßenbau, Bern

Contact:

Cities:

Bern :

The City of Bern is the capital of Switzerland and the capital of the Bern canton. The main municipal activities are governmental and administrative. Industrial activities include the production of fine scientific instruments, textiles, machinery, chemicals, pharmaceuticals, and chocolats. The city has an university and a famous library with many manuscripts and rare books.

Population:

Project was added at 07.02.1997
Project was changed at 17.08.2001

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