PROJECT DESCRIPTION
BACKGROUND
Road transport contributes greatly to the inventory of atmospheric greenhouse gas and air pollution emissions. In general, it is responsible for around 60% of NOx emissions. In regional terms, considering only road transport emissions, traffic on the regional section of the A22 highway causes 41% of NOx emissions.
The EU’s ambient Air Quality Directive provided for the development of plans to limit NOx emissions by 2015. Sustainable mobility foresees the implementation of different components that are essential for meeting air quality standards, such as the creation of low emission zones (LEZs). New concepts of high-impact LEZ represent not only a concrete answer to local air quality issues, but can also contribute to climate change mitigation.
Two specific sets of measures (i.e. the dynamic road capacity and integrated traffic management measures) address the optimisation of traffic flow on the highway, and even on other neighbouring road networks, with the goal of minimising associated energy consumption and greenhouse gas emissions. The objective is to reach a new overall equilibrium within a road transportation system that is able to ensure the same levels of mobility freedom, but with a significantly lower carbon footprint.
OBJECTIVES
The long-term objective of the LIFE BrennerLEC project was the application of the holistic concept of a “low emission corridor” (LEC) for the A22 highway. The project aimed to implement and validate a set of measures to provide clear environmental benefits, in terms of the abatement of air pollution emissions to help implement the Air Quality Directive, the abatement of noise pollution, and the abatement of greenhouse gas emissions within the context of the Roadmap to a Single European Transport Area - Towards a competitive and resource efficient transport system.
The project would carry out extensive monitoring to consolidate a knowledge base (with particular attention to certain environmental indicators, such as black carbon), and the development of environmental policy and legislation in highway environments. After the creation of the pilot-scale Brenner LEC, the project team would determine speed limits in the area based on the use of a proactive approach, with reduced speed limits based on forecasts of pollutant concentrations and traffic flows.
Forecasts of pollutant concentrations would be carried out using an innovative meteorological and pollutant dispersion model, while forecasts of traffic flows will be done with transport flux models. The objective is to obtain the best compromise in terms of environmental benefits, quality of service (including road safety), and user acceptance by means of proactive approaches.
Specific aims were to implement:
- Dynamic speed limits management, to be applied to light vehicles as a function of the current and predicted air quality conditions;
- Dynamic road capacity management, with a temporarily third lane available during highly-saturated traffic conditions; and
- Dynamic integrated traffic management, based on current and predicted conditions.
RESULTS
The LIFE BrennerLEC project improved the environmental and health impact of traffic flows on the Brenner axis, a stretch of the A22 motorway. It established a test stretch on which it implemented a low emissions corridor – i.e. traffic control measures were introduced that reduced emissions of air pollutants without restricting the circulation of vehicles. The measures thus lower the adverse impact of traffic on the local population’s health and protect the Alpine environment, while also increasing traffic safety and capacity.
The project carried out nearly 5 500 hours of tests, generating significant data on the environmental, traffic flow and safety benefits of the control measures. Three measures were tested:
- Dynamic road capacity management to reduce speed limits according to levels of traffic flow and temporarily introduce an additional third lane during busy periods;
- Dynamic speed limits management to be applied to light vehicles according to current and forecast air quality conditions; and
- Dynamic integrated traffic management to improve coordination and management of travel information channels in urban areas to guide road users on recommended routes.
The control measures were mostly based on variable speed limits targeting mainly diesel passenger cars that typically travel at higher speeds and therefore produce higher NOx emissions than heavy trucks, which already travel at the optimal speed. The project helped define how to use most effectively such traffic management measures at the least inconvenience to road users – i.e. measures must be proportional. For example, variable speed limits should only be set when real-time and predicted traffic, weather, and air quality conditions indicate that they are likely to achieve valuable benefits.
The project team also created a complex, intelligent traffic system to allow the traffic management centre of the A22 dynamically activate the variable speed limits. The forecasting function uses data integration provided by the Open Data Hub2, an open platform developed by the project that collects relevant sensor measurements. The ‘traffic state machine’ determines the traffic conditions on a real-time basis and suggests the variable speed limits according to the congestion levels. Data on traffic-generated emissions, weather forecasts and atmospheric stability, and estimations of the nitrogen oxides concentrations are evaluated to determine when these limits are needed. The system also supports the dynamic integrated management of traffic flow between the motorway and the main urban centres of the region – e.g. for re-routing transit vehicles.
In spite of the impact of the Covid-19 pandemic on mobility, specific results included:
In free flow conditions
- 10% reduction of roadside NO2 concentrations with an average speed reduction of 14 km/h.
- 8% reduction of CO2 emissions and a 16% reduction of NO2 emissions in times of high traffic volumes.
In highly congested traffic conditions
- 10% reduction of travel times with similar traffic volumes and fewer traffic jams.
- Significant improvement of traffic safety conditions (accident rate nearly zero with active variable speed limits).
To ensure the long-term benefits of the project, the BrennerLEC results formed the basis for the low-emission Brenner Digital Corridor, which aims to extensively replicate the tested control measures (in conjunction with other measures) on the entire A22 motorway. The corridor will benefit from a future cooperative intelligent transport system hybrid infrastructure.
The impact of the measures, however, depends on the level of compliance of drivers. The project therefore assessed the value of enforcement systems, while at the same recognising the need to encourage drivers to observe the limits voluntarily. It developed a reward initiative based on a gamification app that demonstrated the great potential of such encouragement.
Finally, the project proposed methodology for identifying motorway stretches that would most benefit from the BrennerLEC measures and for optimising the cost-benefit ratio. The work will be carried out in cooperation with the Austrian and German motorway operators. Other relevant topics will be explored, such as controlling entering and leaving traffic flows. Assessment of the current motorway situations in other Member States has also highlighted the need to upgrade and implement the reference EU regulation so that drivers have a consistent experience along the entire Brenner Corridor.
Further information on the project can be found in the project's layman report (see "Read more" section).
