arXiv subjects

Nicolas Koch

Publications and source records attributed to Nicolas Koch.

5 recordsLinked to original sources

arXiv2023

Using machine learning to understand causal relationships between urban form and travel CO2 emissions across continents

Climate change mitigation in urban mobility requires policies reconfiguring urban form to increase accessibility and facilitate low-carbon modes of transport. However, current policy research has insufficiently assessed urban form effects on car travel at three levels: (1) Causality -- Can causality be established beyond theoretical and correlation-based analyses? (2) Generalizability -- Do relationships hold across different cities and world regions? (3) Context specificity -- How do relationships vary across neighborhoods of a city? Here, we address all three gaps via causal graph discovery and explainable machine learning to detect urban form effects on intra-city car travel, based on mobility data of six cities across three continents. We find significant causal effects of urban form on trip emissions and inter-feature effects, which had been neglected in previous work. Our results demonstrate that destination accessibility matters most overall, while low density and low connectivity also sharply increase CO$_2$ emissions. These general trends are similar across cities but we find idiosyncratic effects that can lead to substantially different recommendations. In more monocentric cities, we identify spatial corridors -- about 10--50 km from the city center -- where subcenter-oriented development is more relevant than increased access to the main center. Our work demonstrates a novel application of machine learning that enables new research addressing the needs of causality, generalizability, and contextual specificity for scaling evidence-based urban climate solutions.

cs.LG↗

arXiv2023

Shared Mobility in Berlin: An Analysis of Ride-Pooling with Car Mobility Data

In face of the threat of a climate catastrophe and the resulting urgent need for decarbonization together with the widespread emergence of the sharing economy, shared pooled mobility has been suggested as an alternative to private vehicle use. However, until now all of its real-life implementations have served a niche market, adjacent to taxi services. To better understand this discrepancy, as well as the potential of pooled mobility, we have here simulated and analyzed pooled mobility on the street network of Berlin with car trip data as input for ride requests. We measure the rate of sharable trips, the relative travel time of passengers, the average occupancy of the vehicles, the relatively driven distance compared to driving with a private vehicle. We observe that for requests in the city center of Berlin it is possible to serve all mobility requests currently done by car, with around 4700 vehicles. The travel time is around 1.34 higher than with a private vehicle, the vehicle's occupancy increases to 2.6. The driven distance is reduced by 65%. In the whole area of Berlin we observe that a ride-pooling system with 10000 vehicles can serve 60% of the trips. The travel time is 1.4 times higher than with a private vehicle, the occupancy gets three and the driven distance is reduced by 40%.

stat.AP↗

arXiv2023

Heat increases experienced racial segregation in the United States

Segregation on the basis of ethnic groups stands as a pervasive and persistent social challenge in many cities across the globe. Public spaces provide opportunities for diverse encounters but recent research suggests individuals adjust their time spent in such places to cope with extreme temperatures. We evaluate to what extent such adaptation affects racial segregation and thus shed light on a yet unexplored channel through which global warming might affect social welfare. We use large-scale foot traffic data for millions of places in 315 US cities between 2018 and 2020 to estimate an index of experienced isolation in daily visits between whites and other ethnic groups. We find that heat increases segregation. Results from panel regressions imply that a week with temperatures above 33{\deg}C in a city like Los Angeles induces an upward shift of visit isolation by 0.7 percentage points, which equals about 14% of the difference in the isolation index of Los Angeles to the more segregated city of Atlanta. The segregation-increasing effect is particularly strong for individuals living in lower-income areas and at places associated with leisure activities. Combining our estimates with climate model projections, we find that stringent mitigation policy can have significant co-benefits in terms of cushioning increases in racial segregation in the future.

econ.GN↗

arXiv2020

Effect of pop-up bike lanes on cycling in European cities

The bicycle is a low-cost means of transport linked to low risk of COVID-19 transmission. Governments have incentivized cycling by redistributing street space as part of their post-lockdown strategies. Here, we evaluate the impact of provisional bicycle infrastructure on cycling traffic in European cities. We scrape daily bicycle counts spanning over a decade from 736 bicycle counters in 106 European cities. We combine this with data on announced and completed pop-up bike lane road work projects. On average 11.5 kilometers of provisional pop-up bike lanes have been built per city. Each kilometer has increased cycling in a city by 0.6%. We calculate that the new infrastructure will generate $2.3 billion in health benefits per year, if cycling habits are sticky.

physics.soc-ph↗

arXiv2020

Effects of thermal inversion induced air pollution on COVID-19

Air pollution is a threat to human health, in particular since it aggravates respiratory diseases. Early COVID-19 outbreaks in Wuhan, China and Lombardy, Italy coincided with high levels of air pollution drawing attention to a potential role of particulate matter and other pollutants in infections and more severe outcomes of the new lung disease. Both air pollution and COVID-19 outcomes are driven by human mobility and economic activity leading to spurious correlations in regression estimates. We use district-level panel data from Belgium, Brazil, Germany, Italy, the UK, and the US to estimate the impact of daily variation in air pollution levels on COVID-19 infections and deaths. Using random variation in air pollution generated by thermal inversions, we rule out that changes in mobility and economic activity are driving the results. We find that a 1%-increase in air pollution levels over the three preceding weeks leads to a 1.5% increase in weekly cases. A 1%-increase in air pollution over four weeks leads to 5.1% more COVID-19 deaths. These results indicate that short-term measures to reduce air pollution can help mitigate the health damages of the virus.

physics.soc-ph↗