Regulated and unregulated emissions from Euro VI Diesel and CNG heavy-duty vehicles
This study compares emissions from Euro VI-D Diesel and CNG buses across temperatures from -7 °C to 35 °C. Pollutants including NOx, THC, CH, CO, NH, NO, HCHO, Solid Particle Number larger than 23 nm (SPN23) and larger than 10 nm (SPN10) were measured. Both buses complied with Euro VI-D but exceeded European Commission's proposed Euro 7 limits, notably for NOx and SPN10. The CNG bus also surpassed NH, CO, and CH limits, while the Diesel exceeded NO limits. High NH emissions were observed from CNG (up to 0.320 g/kWh), with Diesel reporting lower levels (up to 0.021 g/kWh). HCHO emission from both vehicles were very low. SPN23 was under limits, but SPN10 exceeded Euro 7 limits at cold start tests. CNG's CH and NO emissions constituted up to 4.6% and 3.5% of CO equivalent, respectively. Diesel bus showed negligible CH but NO emissions represented up to 37% of CO equivalent.
Who would continue to work from home in Hong Kong as the COVID-19 pandemic progresses?
This study aims a more thorough understanding of individuals' motivations and determinants of working from home (WFH) at various phases of the pandemic. To achieve this research goal, we analyze attitudes towards WFH, the profiles of various types of workers engaged in WFH, and the determinants of the current and future expected frequency of WFH among 816 workers in Hong Kong. We identify four types of teleworkers: (1) those with little employer support, (2) those distracted with tech problems, (3) those with good home office, and (4) those with substantial employer support. Separate latent-class choice models present that WFH frequencies in early phases of the pandemic (and at the moment), attitudes towards WFH, and certain constraining/facilitating factors affect the (expected) frequency of WFH. This study provides valuable insights into the types of teleworkers and the determinants of WFH, which will help policymakers create ways to encourage (or discourage) the future frequency of WFH.
Household hurricane evacuation during a dual-threat event: Hurricane Laura and COVID-19
This study explores household-level evacuation decision-making in response to Hurricane Laura, in a context where hurricane risk reduction measures contradicted COVID-19 risk reduction measures. Data were collected using a mail-based survey approach from households along the coast of Texas and Louisiana to explore drivers of and barriers to evacuation, including COVID-19 measures such as negative affect, risk perceptions, protective actions, and exposure. Testing for direct and indirect effects among the drivers of and barriers to evacuation, we find that many of our COVID-19 measures did not have a direct effect on evacuation but did have indirect effects through other factors. We also found evidence of both direct and indirect relationships with regards to more conventional drivers of evacuation found in the literature. We close with a discussion of the limitations and implications of this study.
Role of vehicular emissions in urban air quality: The COVID-19 lockdown experiment
While the decrease in air pollutant concentration during the COVID-19 lockdown is well documented, neighborhood-scale and multi-city data have not yet been explored systematically to derive a generalizable quantitative link to the drop in vehicular traffic. To bridge this gap, high spatial resolution air quality and georeferenced traffic datasets were compiled for the city of London during three weeks with significant differences in traffic. The London analysis was then augmented with a -analysis of lower-resolution studies from 12 other cities. The results confirm that the improvement in air quality can be partially attributed to the drop of traffic density, and more importantly quantifies the elasticity (0.71 for NO & 0.56 for PM) of their linkages. The findings can also inform on the future impacts of the ongoing shift to electric vehicles and micro-mobility on urban air quality.
Investigation of a river-tunnel effect on PM concentrations in New York City subway stations
It is well-documented that subway stations exhibit high fine particulate matter (PM) concentrations. Little is known about the potential of river-tunnels to increase PM concentrations in subways. We hypothesized a "river-tunnel" effect exists: Stations adjacent to poorly ventilated tunnels that travel beneath rivers exhibit higher PM concentrations than more distant stations. Accordingly, the PM concentrations were monitored at stations adjacent to and two- and three-stations distant from the river-tunnel. Multivariate linear regression analysis was conducted to disentangle how proximity to a river-tunnel and other factors (e.g., depth) influence concentrations. Stations adjacent to a river-tunnel had 80-130% higher PM concentrations than more distant stations. Moreover, distance from a river-tunnel was the strongest PM-influencing factor This distance effect was not observed at underground stations adjacent to a river-bridge. The "river-tunnel" effect explains some of the inter-station variability in subway PM concentrations. These results support the need for improving ventilation systems in subways.
Pandemic impacts on public transport safety and stress perceptions in Nordic cities
COVID-19 has brought severe disruption and demand suppression to mobility, especially to public transport (PT). A key challenge now is to restore trust that PT is safe again. This paper investigates pandemic impacts on PT safety and stress perceptions in three Nordic cities, drawing on 2018 and 2020 survey data analysed in structural equation models. While finding modest pandemic effects on safety and stress perceptions overall, strong heterogeneities exist across gender, age and geographic categories. Women perceive less PT safety and more stress, especially during the pandemic. Older adults reduced PT more during the pandemic and perceived no stress reduction like younger adults. Stockholm travellers feel less safe and more stressed than in Oslo and Bergen, whilst pandemic PT use and perceived safety reductions are least in Bergen. The paper discusses the long-term implications for theory and policy across multiple mobility scenarios accounting for modal change and travel demand uncertainties.
The COVID-19 pandemic and the future of telecommuting in the United States
This study focuses on an important transport-related long-term effect of the COVID-19 pandemic in the United States: an increase in telecommuting. Analyzing a nationally representative panel survey of adults, we find that 40-50% of workers expect to telecommute at least a few times per month post-pandemic, up from 24% pre-COVID. If given the option, 90-95% of those who first telecommuted during the pandemic plan to continue the practice regularly. We also find that new telecommuters are demographically similar to pre-COVID telecommuters. Both pre- and post-COVID, higher educational attainment and income, together with certain job categories, largely determine whether workers have the option to telecommute. Despite growth in telecommuting, approximately half of workers expect to remain unable to telecommute and between 2/3 and 3/4 of workers expect their post-pandemic telecommuting patterns to be unchanged from their pre-COVID patterns. This limits the contribution telecommuting can make to reducing peak hour transport demand.
The disparate impact of COVID-19 pandemic on walking and biking behaviors
This study sought to assess changes in active transportation behaviors due to the COVID-19 pandemic, in addition to identifying the disparate impacts between sociodemographic groups. A survey was conducted in November 2020, which collected responses from 1,000 Michigan residents statewide regarding walking and biking behaviors before, during, and anticipated post-pandemic. The survey found that people who walked or biked frequently for recreation before the pandemic maintained or increased their activities during the pandemic. More importantly, the survey also revealed differing pandemic-related impacts on walking and biking behaviors between sociodemographic groups. Specifically, people from underprivileged sociodemographic groups, such as those who are older, have lower education or income level, or identify as a minority, were less active in general before the pandemic, and these walking and biking behavior gaps were exacerbated by the pandemic. Furthermore, the elevated negative impacts on these sociodemographic groups were anticipated to continue in the future.
Insights into the long-term effects of COVID-19 responses on transportation facilities
The impacts of COVID-19 on transportation sector have received a substantial research attention, however, less is known about localized COVID-19 responses that provided safe space for mobility and other daily activities. We applied logistic regression and text mining approaches on the Shifting Streets COVID-19 Mobility Dataset to explore the long-term outcomes of the localized responses. We explored the purpose, affected space, function, and implementation approach. We found that responses instituted for economic recovery and public health are less likely to be long-term, while responses meant to improve safety or bicycle/pedestrian mobility are more likely to be long-term. Further, operational or regulatory responses are less likely to be long-term. Additionally, responses affecting curb space are more likely to be long-term than those affecting other right-of-way areas. Text-mining of responses' narratives revealed key patterns for both short-term and long-term outcomes. Study findings showcase the possible design and operations changes during post-COVID-19 era.
Longitudinal and spatial analysis of Americans' travel distances following COVID-19
Travel has become less common due to COVID-19. While prior research has discussed recent travel changes for Americans in multiple ways, few have examined the adjusted travel that has been sustained since March 2021. In addition, little is known about changes in Americans' travel patterns in trips by distance. In this research, we asked two questions: 1) How have the numbers of trips by distance changed since 2019? and, 2) What are the geospatial patterns of the changes? Data from mid-March to mid-September 2021 indicates a 7% decrease in the number of trips and a 14.5% increase in people staying home. People traveled less except for those in the middle U.S. states, from North Dakota to Texas, as vertically aligned. Staying home more seemed to occur mainly in the South. Trips between 50 and 500 miles increased nationwide. COVID-19 has had different levels of impact on trips of different distance ranges.
Equity in temporary street closures: The case of London's Covid-19 'School Streets' schemes
School Streets are a street space reallocation scheme that has proliferated since the beginning of the Covid-19 pandemic in the UK, reducing motor traffic on streets outside many schools. Utilising a minimum-standards approach to equity, this paper examines the distribution of School Streets closures across social and environmental indicators of equity, and spatially across London's administrative geography. Using a multi-level regression analysis, we show that although School Streets have been equally distributed across several socio-demographic indicators, they are less likely to benefit schools in car-dominated areas of poor air quality, and their spatial distribution is highly unequal. This study presents an example of using environmental and spatial variables alongside more typical sociodemographic indicators in measuring the equity of school travel provision. For policymakers, the findings signal the need to implement complementary policies that can benefit schools with worse air quality, and to accelerate School Street implementation in slower districts.
Neighborhood, built environment and resilience in transportation during the COVID-19 pandemic
COVID-19 has swept the world, and the unprecedented decline in transit ridership has been noticed. However, little attention has been paid to the resilience of the transportation system, particularly in medium-sized cities. Drawing upon a light rail ridership dataset in Salt Lake County from 2017 to 2021, we develop a novel method to measure the vulnerability and resilience of transit ridership using a Bayesian structure time series model. The results show that government policies have a more significant impact than the number of COVID-19 cases on transit ridership. Regarding the built environment, a highly compact urban design might reduce the building coverage ratio and makes transit stations more vulnerable and less resilient. Furthermore, the high rate of minorities is the primary reason for the drops in transit ridership. The findings are valuable for understanding the vulnerability and resilience of transit ridership to pandemics for better coping strategies in the future.
Public transit cuts during COVID-19 compound social vulnerability in 22 US cities
The COVID-19 pandemic has severely impacted public transit services through plummeting ridership during the lockdown and subsequent budget cuts. This study investigates the equity impacts of reductions in accessibility due to transit service cuts during COVID-19 and their association with urban sprawl. We evaluated transit access to food and health care services across 22 US cities in three phases during 2020. We found stark socio-spatial disparities in access to basic services and employment in food and health care. Transit service cuts worsened accessibility for communities with multiple social vulnerabilities, such as neighborhoods with high rates of poverty, low-income workers, and zero-vehicle households, as well as poor neighborhoods with high concentrations of black residents. Moreover, sprawled cities experienced greater access loss during COVID-19 than compact cities. Our results point to policies and interventions to maintain social equity and sustainable urban development while benefiting diverse social groups during disruptions.
The impact of perceived racism on walking behavior during the COVID-19 lockdown
The COVID-19 pandemic lockdown has had a significant impact on people's travel behavior. The level of this impact has been unevenly distributed among different population groups. The recent rise in anti-Asian racism implies that Asians have faced increased stress during the pandemic. As a result, the impact on their travel behavior is likely to differ from other ethnic groups. We examined this hypothesis by focusing on the impact of the pandemic on walking behavior. We collected survey data in Melbourne, Australia, during the pandemic lockdown, and analyzed the data using a Structural Equation Model approach. The results suggest that Asians experienced a significantly higher level of discrimination than other racial groups and were less likely to increase walking than White people. We also found that neighborhood cohesion helped alleviate perceived discrimination and promote walking. This study offers new insights into the role of racism in travel behavior.
Potential long-term effects of Covid-19 on telecommuting and environment: An Italian case-study
To contain the sudden spread of SARS-CoV-2, many governments encouraged people to work from home, generating an unprecedented diffusion of this activity. Furthermore, Covid-19 has induced drastic changes in everyday life and travel habits, which might persist in the future. This paper aims to understand and estimate the potential long-term impacts of telework on the environment due to the pandemic, by analyzing factors affecting the frequency of telecommuting, the mode choice for traveling to work, and pollutant emissions generated by these trips. Data from a mobility survey administered in Padova (Italy) was used. Results indicate that Covid-19 could cause a rebound effect reversing the positive impacts of working from home, since, even if the number of trips could be reduced, many shifts towards non-sustainable travel modes could occur. The promotion of telework should be combined with measures fostering sustainable travel habits to pave the way towards a future green mobility.
Benchmarking the driver acceleration impact on vehicle energy consumption and CO emissions
The study proposes a methodology for quantifying the impact of real-world heterogeneous driving behavior on vehicle energy consumption, linking instantaneous acceleration heterogeneity and CO emissions. Data recorded from 20 different drivers under real driving are benchmarked against the Worldwide Harmonized Light Vehicle Test Cycle (WLTC), first by correlating the speed cycle with individual driver behavior and then by quantifying the CO emissions and consumption. The vehicle-Independent Driving Style metric (IDS) is used to quantify acceleration dynamicity, introducing driving style stochasticity by means of probability distribution functions. Results show that the WLTC cycle assumes a relatively smooth acceleration style compared to the observed ones. The method successfully associates acceleration dynamicity to CO emissions. We observe a 5% difference in the CO emissions between the most favourable and the least favourable case. The intra-driver variance reached 3%, while the inter-driver variance is below 2%. The approach can be used for quantifying the driving style induced emissions divergence.
Evolution of European light-duty vehicle CO emissions based on recent certification datasets
A new vehicle testing procedure (WLTP - Worldwide Light duty vehicle Test Procedure) was introduced in the European Union (EU) in 2017. In order to examine its actual impact on CO emissions for different vehicle technologies and categories, this study analysed data from vehicles certified and registered in the EU in 2019 and 2020. It was found that in average, for all vehicles sold in 2020, the increase in CO emissions due to the intoduction of the WLTP was 21% for passenger cars and 27% for vans. Also that diesel vehicles are impacted more than gasoline ones and that the impact on conventional hybrid vehicles is 27% and plug-in hybrid vehicles between 0% (in 2020) and 11% (in 2019). Models employed revealed that the increase in CO is mainly due to the higher test masses and more realistic road load coefficients of WLTP that result in higher cycle energy demands. Moreover, results confirmed that the impact of the WLTP's introduction is in line, both in terms of absolute increase and variability, with model-based predictions performed before fleet-wide data were made available.
Aircraft noise and environmental equity in Montréal: A comparison of noise indicators and an analysis of the impacts of COVID-19
From an environmental equity perspective, the aim of this paper is twofold. First, we want to verify to what extent vulnerable population groups resided in areas exposed to high levels of aircraft noise before and during the COVID-19 pandemic (2019 and 2020) in the Montréal census metropolitan area. Second, we want to identify whether the use of an aircraft noise indicator rather than another generates significant variations in the results and consequently in terms of affected areas and populations. With the IMPACT web-application, we model aircraft noise contours from three cumulative ( , , ) and a single-event ( ) metrics. The model's input data are retrieved by a website for flight tracking. Next, four variables are extracted from the 2016 Statistics Canada census at a fine scale level (dissemination areas): that is, the percentages of low-income individuals, visible minorities, children under 15 years old, and individuals aged 65 and over. The results show a significant drop in population exposed to aircraft noise in 2020 compared to 2019. In addition, the estimates of populations impacted by aircraft noise differ from one indicator to the next. The logistic regression models indicate that the inequities are inconsistent between cumulative and single-event metrics.
Wishful thinking? Addressing the long-term implications of COVID-19 for transport in Nigeria
With their inherent economic and infrastructure challenges, developing countries must assess commuters' travel behaviour and establish whether consumers' desire for sustainable transportation is feasible or merely wishful thinking. Using a qualitative research design, these issues were explored based on semi-structured interviews conducted with 72 participants across the six geopolitical zones of Nigeria. Findings suggest that the desires and dreams of the commuters are great, and they want to reduce their journeys, work from home, and do online shopping. However, when they consider the inherent challenges, they can only hope for a better future. COVID-19 has impacted the ownership or use of motorised and non-motorised transport, but this is also influenced by affordability, convenience, and awareness. Likewise, there are long-term effects on home and work location choices, but this is further influenced by the large informal economy of the country, job accessibility and the infrastructural developments across the country.
Executive orders or public fear: What caused transit ridership to drop in Chicago during COVID-19?
The COVID-19 pandemic has induced significant transit ridership losses worldwide. This paper conducts a quantitative analysis to reveal contributing factors to such losses, using data from the Chicago Transit Authority's bus and rail systems before and after the COVID-19 outbreak. It builds a sequential statistical modeling framework that integrates a Bayesian structural time-series model, a dynamics model, and a series of linear regression models, to fit the ridership loss with pandemic evolution and regulatory events, and to quantify how the impacts of those factors depend on socio-demographic characteristics. Results reveal that, for both bus and rail, remote learning/working answers for the majority of ridership loss, and their impacts depend highly on socio-demographic characteristics. Findings from this study cast insights into future evolution of transit ridership as well as recovery campaigns in the post-pandemic era.
Smartphone-based services, perceived accessibility, and transport inequity during the COVID-19 pandemic: A cross-lagged panel study
Individuals have experienced various degrees of accessibility loss during the COVID-19 pandemic, which may consequently influence transport equity. However, conventional measurements of accessibility cannot capture individual experiences and perceptions of accessibility. Moreover, since many daily necessities and services can only be acquired online during the pandemic, the ease of using smartphone-based services play an essential role in people's everyday lives. Therefore, this paper investigates the relationship between the ease of using smartphone-based services, perceived accessibility, and perceived transport equity during the pandemic. Based on 186 family interviews, a panel survey with 569 respondents was conducted monthly from February to October 2020 in Kunming, China, and a three-wave cross-lagged panel model was developed to understand the causal relationship between the three constructs. The results indicate that the ease of using smartphone-based services dominantly influence transport equity in the early phase of the pandemic, but its effect faded after the lifting of travel restrictions. Perceived accessibility to services appears a sound indicator for transport equity in the new normal, but perceived accessibility and transport equity are not strongly associated when staying at home is perceived as desirable. Moreover, we found that contemporary practices of smartphone-based new mobility services only favour those who already have convenient access to services and have further excluded and marginalised disadvantaged populations, which urgently require policy interventions.