In urban areas, traffic is one of the biggest sources of noise. Due to the settlement structure, a particularly large number of people are affected by traffic noise. The increasing spread of electric mobility could significantly reduce this burden, although there has been a lack of scientific basis so far. Since 2024, TCS has been investigating together with Empa, as part of the Nexus research project, how the noise levels of electric cars and combustion engines differ under different driving conditions. The measurement drives of the first phase of Nexus showed that electric cars are significantly quieter during acceleration than combustion engines of the same category (press release of June 24, 2025).
Traffic nodes in Fribourg and Zurich under scrutiny
The test drives of the first Nexus phase took place on the track of the TCS Driving Center Stockental, and thus not in normal road traffic. In the second phase of the Nexus project, Empa and TCS took it a step further by applying the insights from the test drives to real traffic situations. Acoustic models were developed for all test vehicles to calculate how much noise a vehicle generates depending on speed and acceleration. Subsequently, traffic flows at four intersections and roundabouts in the cities of Fribourg and Zurich were measured (Champ-des-Fontaines, Sainte-Thérèse, Albisriederplatz, and Sihlporte). The driving behaviour of individual vehicles was recorded using drone footage, and the speed, acceleration, and driving paths of the vehicles were evaluated.
The noise advantage grows at peak times
With the data from the test drives combined with real traffic flows, a mathematical model was created: What if all driving movements at the intersections took place with electric cars? The result is clear: On average, electric cars are 1.5 decibels quieter compared to combustion-only fleets at the same intersections and roundabouts. In everyday traffic, cars often have to brake and start again at intersections. At such stopping points, the difference between electric cars and combustion engines is even up to 3 decibels, equivalent to a halving of the noise. It is also relevant whether there is a lot of traffic. At Zurich’s Albisriederplatz, electric cars were on average 0.9 decibels quieter at low traffic volumes. During peak times, the difference increased to 2.2 decibels compared to the combustion-only model.
At the two intersections in Fribourg, the impact of reducing the signalled maximum speed from 50 to 30 kilometres per hour was examined. The difference in noise emissions between combustion engines and electric cars changed only slightly. The additional noise advantage of electric cars amounted to about 0.5 decibels, as rolling noise also plays a significant role at 30 km/h.
For Sascha Grunder, Head of Test & Technology at TCS, the perception of residents was at the forefront of the second phase of the Nexus project: "The study shows that noise-burdened people living near intersections stand to benefit particularly from the electrification of mobility." Reto Pieren, Group Leader of Environmental Acoustics at Empa, also assesses the results positively: "For the first time, we were able to quantify the noise reduction potential of electric cars in complex traffic situations. This was achieved thanks to the use of modern measurement methods and simulations specially developed for this purpose. Next, we will take a closer look at the importance of tyres and road surfaces."
Nexus III follows next year
The detailed results of the study will be presented this week at the specialist conference Forum Acusticum in Graz. At the same time, data evaluation for the third phase of Nexus is ongoing. In June, measurement drives with electric cars and combustion engines took place on public roads in Aargau. This phase investigates the extent to which different tyre types and road surfaces affect noise emissions across various driving profiles. The results of these tests are expected to be published in mid-2027.
Press Contact:
Marco Wölfli, Media Spokesperson TCS
Tel. 058 827 34 03
marco.woelfli@tcs.ch