Traffic study B15

Initial Situation

The federal highway B 15, or B 15neu, serves as an important regional north-south connection for the major centers of Regensburg, Landshut, and Rosenheim. In the Landshut area, it is currently heavily used, with traffic volumes between 20,000 and 25,000 vehicles per day. Due to numerous town passages and a low development standard, the existing B 15 is no longer suitable for efficiently and safely handling the traffic volume. For these reasons, it is necessary to conduct a detailed traffic study of the East-South Bypass Landshut for the subsequent planning stages.

The East-South Bypass Landshut consists of the eastern bypass between the A 92 motorway and the B 299, and the southern bypass between the B 299 and the B 15. The planning scenarios 1b and 1c, coordinated in the spatial planning procedure, are examined in detail.

The basis for the study is the Bavarian State Traffic Model (LVM-By). The model meets all standard requirements for a traffic demand model (e.g., according to the Handbook for the Design of Road Traffic Facilities – HBS 2015 of the Research Society for Roads and Transport – FGSV).

Task Definition

For the traffic study, various levels of content analysis must be linked. It is necessary to establish a quantitative basis in the form of a traffic volume framework. This includes data collection, the development of the traffic model, and the representation of the projected situation in the forecast year (here, 2035). This forecast scenario forms the basis for the various network scenarios to be examined.

For each represented traffic situation, the actual traffic study is then carried out through targeted evaluation and preparation of the model results. The traffic volume framework is generated using PTV software Visum. Capacity verifications are conducted according to the HBS and, if necessary, through microsimulation using PTV Vissim.

Approach

A subnet is generated from the Bavarian State Traffic Model, and the network is adjusted and refined. Traffic surveys are conducted at numerous intersections, which are then used to calibrate and validate the model. Subsequently, the 2035 reference scenario is developed, and the planning scenarios are represented using the VISUM Scenario Manager, with the macroscopic traffic study carried out accordingly. At selected intersections, capacity analyses are performed for each scenario, and, if necessary, a microsimulation is conducted.

In addition, traffic parameters are determined for noise calculations according to RLS 19 and RLS 90, as well as greenhouse gas emissions based on current standards. All results are documented in graphical, tabular, and written form, and the client is supported in objection management within the framework of the formal planning approval process.

Results

The results indicate that routing the B 15neu along the alignment of planning scenario 1c provides a significantly higher relief effect on the B 299 (Konrad-Adenauer-Straße in Landshut) for both passenger and heavy traffic. For the sections of the B 15, both alignments (planning scenarios 1b and 1c) show similar relief effects. Therefore, the inner-city network of Landshut experiences an overall positive impact from the East-South Bypass in both planning scenarios 1b and 1c.

Capacity analyses according to HBS 2015 at selected intersections show a traffic quality level of D on the B 299 in the reference scenario. Due to traffic increases in the scenarios—resulting from the attractive effect of the B 15neu—traffic quality on the B 299 in morning and evening peak hours sometimes exceeds the target level D.

A four-lane expansion of the B 299 would alleviate this issue. However, the problem persists where the road narrows back to two lanes. In the scenarios for planning scenario 1c, no expansion of the B 299 is planned, resulting in corresponding reductions in quality, as the two-lane sections can only achieve reduced speed levels under the projected peak traffic volumes.

The sensitivity analysis shows that even minor changes in peak hour shares can affect traffic quality. Particularly when traffic density is at the borderline between levels D and E, the main effect is a reduced speed with vehicle platooning rather than a full stop-and-go collapse. To verify this, a microscopic traffic flow simulation was conducted for all scenarios and intersections where the calculated quality level would exceed D to E. The simulation demonstrates that no critical traffic conditions occur, and there are no blockages or congestion phenomena.