Measuring Urban Bicyclists\u27 Uptake of Traffic-Related Pollution

Urban bicyclists’ uptake of traffic-related air pollution is still not well quantified, due to a lack of direct measurements of uptake and a lack of analysis of the variation in uptake. This paper describes and establishes the feasibility of a novel method for measuring bicyclists’ uptake of volatile organic compounds (VOC) by sampling breath concentrations. Early results from the data set demonstrate the ability of the proposed method to generate findings for transportation analysis, with statistically significant exposure and uptake differences from bicycling on arterial versus bikeway facilities for several traffic-related VOC. These results provide the first empirical evidence that the usage of bikeways (or greenways) by bicyclists within an urban environment can significantly reduce uptake of dangerous traffic-related gas pollutants. Dynamic concentration and respiration data reveal unfavorable correlations from a health impacts perspective, where bicyclists’ respiration and travel time are greater at higher-concentration locations on already high-concentration roadways (arterials).https://pdxscholar.library.pdx.edu/trec_seminar/1048/thumbnail.jp

Modeling the Effects of Congestion on Fuel Economy for Advanced Power Train Vehicles

This paper describes research undertaken to establish plausible fuel-speed curves (FSC) for hypothetical advanced power train vehicles. These FSC are needed to account for the effects of congestion in long-term transportation scenario analysis considering fuel consumption and emissions. We use the PERE fuel consumption model with real-world driving schedules and a range of vehicle characteristics to estimate fuel economy (FE) in varying traffic conditions for light-duty internal combustion engine (ICE) vehicles, hybrid gas-electric vehicles (HEV), fully electric vehicles (EV), and fuel cell vehicles (FCV). FSC are fit to model results for each of 145 hypothetical vehicles. Analysis of the FSC shows that advanced powertrain vehicles are expected to perform proportionally better in congestion than ICE vehicles (when compared to their performance in free-flow conditions). HEV are less sensitive to average speed than ICE vehicles, and tend to maintain their free-flow FE down to 20 mph. FE increases for EV and FCV from free-flow conditions down to about 20-30 mph. Beyond powertrain type differences, relative FE in congestion is expected to improve for vehicles with less weight, smaller engines, higher hybrid thresholds, and lower accessory loads (such as air conditioning usage). Relative FE in congestion also improves for vehicle characteristics that disproportionately reduce efficiency at higher speeds, such as higher aerodynamic drag and rolling resistance. In order to implement these FSC for scenario analysis, we propose a bounded approach based on a qualitative characterization of the future vehicle fleet. The results presented in this paper will assist analysis of the roles that vehicle technology and congestion mitigation can play in reducing fuel consumption and emissions from roadway travel

Value of Travel Time Reliability Part II: A Study of Tradeoffs Between Travel Reliability, Congestion Mitigation Strategies and Emissions

Capacity, demand, and vehicle based emissions reduction strategies are compared for several pollutants employing aggregate US congestion and vehicle fleet condition data. We find that congestion mitigation does not inevitably lead to reduced emissions; the net effect of mitigation depends on the balance of induced travel demand and increased vehicle efficiency that in turn depend on the pollutant, congestion level, and fleet composition. In the long run, capacity-based congestion improvements within certain speed intervals can reasonably be expected to increase emissions of CO2e, CO, and NOx through increased vehicle travel volume. Better opportunities for emissions reductions exist for HC and PM2.5 emissions, and on more heavily congested arterials. Advanced-efficiency vehicles with emissions rates that are less sensitive to congestion than conventional vehicles generate less emissions co-benefits from congestion mitigation

Webinar: Impacts of Roadway and Traffic Characteristics on Air Pollution Risks for Bicyclists

Active travel such as walking and bicycling can lead to health benefits through an increase in physical activity. At the same time, more active travelers breath more and so can experience high pollution inhalation rates during travel. This webinar will review the state of knowledge about how roadway and traffic characteristics impact air pollution risks for bicyclists, including the latest PSU research quantifying bicyclists\u27 uptake of traffic-related air pollution using on-road measurements in Portland. The PSU research team including Alex Bigazzi, Jim Pankow, and Miguel Figliozzi quantified bicyclist exposure concentrations on different types of roadways, respiration responses to exertion level, and changes in blood concentrations of pollutants. Implications for planners, engineers, and policy-makers will be discussed, including guidance for more pollution-conscious bicycle network planning and design. Additionally, ways for individual travelers to reduce their air pollution risks will be discussed. This 60-minute webinar is eligible for one hour of training which equals 1 CM or 1 PDH. NITC applies to the AICP for Certification Maintenance credit for each webinar. We will provide an attendance certificate to those who document their professional development hours.https://pdxscholar.library.pdx.edu/trec_webinar/1009/thumbnail.jp

Transportation System Impacts on Bicyclists\u27 Air Pollution Risks: Considerations for System Design and Use

Health risks associated with air pollution uptake while bicycling are often cited as a potential drawback to increased bicycling in cities. This seminar will provide an overview of how roadway and travel characteristics impact bicyclists\u27 uptake of traffic-related air pollution. Specific considerations for planners and designers of urban transportation systems to mitigate risks for travelers will be discussed. In addition, the extent to which bicyclists themselves can unilaterally reduce their pollution uptake will be described. This seminar synthesizes findings from a recently completed doctoral dissertation at Portland State University and from the broader literature.https://pdxscholar.library.pdx.edu/trec_seminar/1017/thumbnail.jp

That Bike is Too Heavy: Merging Bicycling Physics, Human Physiology and Travel Behavior

Are the Biketown bikes too heavy? Does better gear motivate people to cycle more? How much faster will someone go on an e-bike? Although urban cycling is widely known as physically active transportation, the actual physics of cycling have been given little attention in transportation engineering and planning. In contrast, the field of sports science has developed detailed data and models of road bicycle performance, but only for sport and racing cyclists. What can we learn about utilitarian cycling by integrating knowledge of the physical attributes of bicycles and cyclists? This seminar examines the ways in which bicycle physics, and the physiology of cyclists, can influence outcomes of interest to transportation professionals, from speed and stopping distance to cycling frequency and health benefits. Findings will be presented from recent and ongoing studies aiming to quantify these relationships and enhance travel analysis tools with an understanding of the physical aspects of cycling.https://pdxscholar.library.pdx.edu/trec_seminar/1169/thumbnail.jp

Refining GreenSTEP: Impacts of Vehicle Technologies and ITS/Operational Improvements on Travel Speed and Fuel Consumption Curves

This report describes analysis undertaken to establish a method for incorporating traffic operations and ITS strategies into the GreenSTEP model. We first discuss operations impacts on fuel economy and delay from the literature. Then, an investigation of delay adjustments in GreenSTEP shows that different methods of representing delay changes lead to similar (and small) impacts on fuel economy. From this result we establish average speed adjustment by congestion level as the preferred method for incorporating delay effects from operations improvements. An investigation of aggregate traffic operations impacts produces estimates of base speeds without operations improvements, maximum speeds with full operational improvements, and existing deployments by city size for each congestion level. These estimates are made for ramp metering, incident management, traffic signal coordination, and access management strategies. Additionally, a comparison of constant-speed and drive schedule-based fuel-speed curves generates estimates of potential fuel benefits from eco-driving and speed-smoothing traffic management strategies. Results show that the cumulative impact of delay-based operations strategies on fuel economy is small, though speed-smoothing effects can be large. The operations impacts estimates are used to provide guidance for estimates of operations efficacy in delay reductions and speed smoothing for the GreenSTEP model. The proposed implementation strategy includes an efficacy estimates tool for the net effects of operations strategies, and identifies locations in the model where those effects can be included. Traffic operations impacts on travel demand are separately applied as travel demand management inputs to the existing GreenSTEP model

The Impact of Freeway Traffic Conditions on in-Vehicle Exposure to Ultrafine Particulate Matter

There is evidence of adverse health impacts from human exposure to traffic-related ultrafine particulate matter pollution. As more commuters are spending a significant portion of their daily routine inside vehicles, it is increasingly relevant to study exposure levels to harmful pollutants inside the vehicle microenvironment. This study is one of the first research efforts to combine detailed freeway traffic data (at 20 s intervals) and in-vehicle ultrafine particulate (UFP) exposure data under varying vehicle ventilation conditions. Results show that due to negative correlation between traffic speed and density, traffic states have a small but significant impact on in-vehicle UFP concentrations, highest in high traffic flow-high speed conditions or in high traffic density-low speed conditions. Vehicle cabin barrier effects are the primary determinant of in-vehicle exposure concentrations, providing 15% protection with the windows down, 47% protection with the windows up and the vent open, and 83-90% protection with the windows up and the vent closed (more with the air conditioning on). Unique results from this study include the dominance of ventilation over traffic effects on UFP and the non-linear relationships between traffic variables and UFP concentrations. The results of this research have important implications for exposure modeling and potential exposure mitigation strategies

Roadway Determinants of Bicyclist Multi-pollutant Exposure Concentrations

Due to poorly quantified traffic-exposure relationships, transportation professionals are unable to easily estimate exposure differences among bicycle routes for network planning, design, and analysis. This paper estimates the effects of roadway characteristics on bicyclist multi-pollutant exposure concentrations, controlling for meteorology and background conditions. Concentrations of volatile organic compounds (VOC), carbon monoxide (CO), and fine particulate matter (PM2.5) are modeled using high-resolution on-road data. This paper also compares exposure differences on immediately parallel high-traffic/low-traffic facilities and is the first study to quantify VOC exposure differences by facility. Results indicate that average daily traffic (ADT) provides a parsimonious way to characterize the impact of roadway characteristics on bicyclists’ exposure. VOC and CO exposure increased by around 2% per 1,000 ADT, robust to several different regression model specifications. The results have important policy and design implications to reduce bicyclists’ exposure. Separation between bicyclists and motor vehicle traffic is a necessary but not sufficient condition to reduce exposure concentrations; off-street paths are not always low-pollution facilities. Direct comparisons of exposure concentrations on parallel routes shows that minor detours to nearby low-traffic facilities can dramatically reduce exposure to strongly traffic-related pollutants

Dynamic Ventilation and Power Output of Urban Bicyclists

Bicyclist intake of air pollutants is linked to physical exertion levels, ventilation rates, and exposure concentrations. Whereas exposure concentrations have been widely studied in transportation environments, there is relatively scant research linking on-road ventilation with travel conditions and exertion levels. This paper investigates relationships among power output, heart rate, and ventilation rate for urban bicyclists. Heart rate and ventilation rate were measured on-road and combined with power output estimates from a bicycle power model. Dynamic ventilation rates increased by 0.4-0.8% per watt of power output, with a mean lag of 0.8 minutes. The use of physiology (ventilation) monitoring straps and heart rate proxies for dynamic on-road ventilation measurements are discussed. This paper provides for a clearer and more quantitative understanding of bicyclists’ ventilation and power output, which is useful for studies of pollutant inhalation risks, energy expenditure, and physical activity