How opening windows and other measures decrease virus concentration in a moving car

Abstract

PurposeDue to the ongoing Covid-19 pandemic, ventilation in a small cabin where social distancing cannot be guaranteed is extremely important. This study aims to find out the best configuration of open and closed windows in a moving car at varying speeds to improve the ventilation efficiency. The effectiveness of other mitigation measures including face masks, taxi screens and air conditioning (AC) systems are also evaluated.Design/methodology/approachEach window is given three opening levels: fully open, half open and fully closed. For a car with four windows, this yields 81 different configurations. The location of virus source is also considered, either emitting from the driver or from the rear seat passenger. Then three different travelling speeds, 5 m/s, 10 m/s and 15 m/s, are examined for the window opening/closing configurations that provide the best ventilation effect. A study into the effectiveness of face masks is realised by adjusting virus injection amounts; and the simulation of taxi screens and AC system simply requires a small modification to the car model.FindingsThe numerical studies identify the top window opening/closing configurations that provide the most efficient ventilation at different moving speeds, along with a comprehensive ranking list. The results show that fully opening all windows is not always the best choice. Simulations evaluating other mitigation measures confirm good effect of face masks and poor performance of taxi screens and AC systems.Originality/valueThis work is the first large-scale numerical simulation and parametric study about different window opening/closing configurations of a moving car. The results provide useful guides for travellers in shared cars to mitigate Covid-19 transmission risks. The findings are helpful to both individuals' health and society's recovery in the Covid-19 era and they also provide useful information to protect people from other respiratory infectious diseases such as influenza.

COVID-19 transmission and control in land public transport: A literature review

“…Natural ventilation is a low-cost, economical, and energy-saving alternative in land public transportation. It can effectively reduce the infection risk, which has been verified in real cases [67 , 68 , 70] , experiments [35 , 39 , 66] , and modeling [38 , 48 , 50 , [53] , [54] , [55] , 72 , 81 , 82] . When the vehicle is driving, the external airflow generates a pressure distribution over the vehicle - the areas near the front are lower-than-atmospheric pressures, while the areas toward the middle and rear of the vehicle are neutral or higher-than-atmospheric pressures ( Fig.…”

Fate of Exhaled Droplets From Breathing and Coughing in Supermarket Checkouts and Passenger Cars

“…Similarly, fully opening all windows is not always the best choice in an open window passenger car, with one front window and the diagonal rear window open shows the best ventilation efficiency. 57 In such small size passenger cars, the virus generated by front-seated travelers is 5 to 10 times easier to be vented out than the rear-seated travelers. 57 The current simulation used a configuration with windows closed because driving with windows open is rare in Los Angeles, the context of these simulations, as high vehicle speeds induce significant buffeting and road noise effects that impair passenger comfort.…”

“…57 In such small size passenger cars, the virus generated by front-seated travelers is 5 to 10 times easier to be vented out than the rear-seated travelers. 57 The current simulation used a configuration with windows closed because driving with windows open is rare in Los Angeles, the context of these simulations, as high vehicle speeds induce significant buffeting and road noise effects that impair passenger comfort. 58,59 Facemask use Measures that have been implemented in supermarkets and shared-ride vehicles such as facemask use, and implementation of partitions have a significant potential to change droplet nuclei trajectories and deposition patterns.…”

Vehicle Design Strategies to Reduce the Risk of COVID-19 Transmission in Shared and Pooled Travel: Inventory, Typology, and Considerations for Research and Implementation

“…This suggests a general prioritization for objective evaluations of CRVD strategies; specifically, more studies are needed to understand how space conditioning (Ventilation and Air Circulation, Air Filtration and Cleaning), Barriers, and Seating Configuration in shared and pooled vehicles affect COVID-19 aerosol transmission. These studies have started to emerge (30)(31)(32)(33)(34)(35) and are crucial to provide specific guidance for public transport and mobility services operators. Since Air Filtration and Cleaning strategies are less familiar and generally less observable to users, these should be coupled with educational strategies to make users aware that they are in operation and explain how they work (this applies also to Ventilation and Air Circulation measures that are not readily perceived by users, e.g., when mechanical ventilation is supplying fresh air).…”

“…This paper does not make specific recommendations. Expert opinions are not a substitute for objective evaluations of the effectiveness of vehicle design strategies in mitigating the risk of COVID-19 transmission, which are crucial and are beginning to emerge (30)(31)(32)(33)(34)(35). This research was part of a broader study that also included interviews with a small, convenience sample of public transit and shared mobility users, the details of which can be found in the report produced as a deliverable for the funded project (36).…”