conference paper

Dynamic autonomous vehicle fleet operations: Optimization-based strategies to assign AVs to immediate traveler demand requests

Proceedings of the 97th annual meeting of the transportation research board

Publication Date

January 1, 2018

Author(s)

Michael Hyland, Hani Mahmassani

Abstract

The emergence and adoption of fully-autonomous vehicles (AVs) is expected to accelerate certain trends already underway in the transportation sector, such as the growth of shared-use mobility and mobility-on-demand services. This paper models an AV mobility service option wherein a fleet of AVs provide direct origin-destination service to travelers that request rides via a mobile application and expect to be picked up within a few minutes. The underlying problem is highly dynamic and stochastic. The solution strategy consists of repeated solution of an integer program referred to as the AV-traveler assignment problem. As the state of the system changes via dynamic traveler requests entering the system, the AV fleet operator re-solves the static AV-traveler assignment problem to assign and reassign AVâ??s to travelers. Given that AV fleets will need to compete with the personal vehicle in terms of cost and quality of service, the authors present and compare several optimization-based strategies to operate an AV fleet with the twin objectives of minimizing costs and maximizing quality of service. To compare the AV fleet operational strategies, the authors perform an extensive computational analysis using an agent-based simulation tool. The results indicate that using optimization-based heuristic strategies rather than simple first-come, first-served (FCFS) heuristics, and incorporating all AVs in the AV-traveler assignment problem (not only currently idle AVs) improves the efficiency of the AV fleet in terms of fleet miles and traveler wait times. The simulation results also indicate that the most-effective AV-traveler assignment strategy results in 6-7% of all fleet miles to be empty for spatially clustered traveler origins and destinations, compared with 11-15% for traveler origins and destinations that are uniformly distributed.

Suggested Citation

Michael Hyland and Hani S. Mahmassani (2018) “Dynamic autonomous vehicle fleet operations: Optimization-based strategies to assign AVs to immediate traveler demand requests”, in Proceedings of the 97th annual meeting of the transportation research board, p. 11p.

published journal article

Shared school transportation: determinants of carpooling as children’s school travel mode in California

Transportation

Publication Date

June 1, 2020

Author(s)

Rezwana Rafiq, Suman Mitra

View published journal article

Abstract

Carpooling has potential as an alternative mode of school transportation along with other viable options, especially at a time when technology continues to increase our reliance upon shared mobility. Unfortunately, our knowledge of carpooling as a school travel mode is very limited. The purpose of this paper is to fill this gap. Using a multinomial logit model, this study presents an analysis of data from the 2012 California Household Travel Survey to assess the effects of various factors, such as trip characteristics, child characteristics, parental or caregiver’s characteristics, household characteristics, and spatial variables on choosing carpooling as a school travel mode. The findings of the study indicate that travel distance is one of the major determinants of carpooling, suggesting that children are more likely to carpool to school as travel distance from home to school increases. The analysis shows that a higher income two-parent two-earner family with a 5–15-year-old female schoolchild is more likely to use carpooling for school trips when compared to other modes of transportation. Parental/caregiver characteristics are also found to be important, as children from households with young, female, higher educated heads are more likely to carpool to school. Results of spatial variables suggest that families living in neighborhoods with higher numbers of schoolchildren are also more likely to carpool. The empirical evidence presented in this study provides useful insight to school districts, policymakers, and other transportation related entities in identifying potential target groups to whom this travel mode could be presented.

Suggested Citation

Rezwana Rafiq and Suman Kumar Mitra (2020) “Shared school transportation: determinants of carpooling as children’s school travel mode in California”, Transportation, 47(3), pp. 1339–1357. Available at: 10.1007/s11116-018-9942-z.

published journal article

Estimating the value of urban green areas: A hedonic pricing analysis of the single family housing market in Los Angeles, CA

Landscape Urban Plann.

Publication Date

March 1, 2012

Author(s)

Jean-Daniel Saphores, Wei Li

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Suggested Citation

Jean-Daniel Saphores and Wei Li (2012) “Estimating the value of urban green areas: A hedonic pricing analysis of the single family housing market in Los Angeles, CA”, Landscape Urban Plann., 104(3-4), pp. 373–387. Available at: 10.1016/j.landurbplan.2011.11.012.

conference paper

Poster: Towards Large-Scale Measurement Study on LiDAR Spoofing Attacks against Object Detection

Proceedings of the 2022 ACM SIGSAC Conference on Computer and Communications Security

Publication Date

November 7, 2022

Author(s)

Takami Sato, Yuki Hayakawa, Ryo Suzuki, Yohsuke Shiiki, Kentaro Yoshioka, Qi Alfred Chen

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Abstract

LiDAR (Light Detection And Ranging) is an indispensable sensor for precise long- and wide-range 3D sensing of the surrounding environment. The recent rapid deployment of autonomous driving (AD) has highly benefited from the advancement of LiDARs. At the same time, the safety-critical application strongly motivates its security research. Recent studies demonstrate that they can manipulate the LiDAR point cloud and fool object detection by shooting malicious lasers against LiDAR scanning. However, prior efforts focus on limited types of LiDARs and object detection models, and their threat models are not clearly validated in the real world. To fill the critical research gap, we plan to conduct the first large-scale measurement study on LiDAR spoofing attacks against a wide variety of LiDARs with major object detectors. To perform this measurement, we first significantly improved the LiDAR spoofing capability (30x more spoofing points than the prior attack) with more careful optics and functional electronics, which allows us to be the first to clearly demonstrate and quantify key attack capabilities assumed in prior works. In this poster, we present our preliminary results on VLP-16 and our research plan.

Suggested Citation

Takami Sato, Yuki Hayakawa, Ryo Suzuki, Yohsuke Shiiki, Kentaro Yoshioka and Qi Alfred Chen (2022) “Poster: Towards Large-Scale Measurement Study on LiDAR Spoofing Attacks against Object Detection”, in Proceedings of the 2022 ACM SIGSAC Conference on Computer and Communications Security. New York, NY, USA: Association for Computing Machinery (CCS '22), pp. 3459–3461. Available at: 10.1145/3548606.3563537.

conference paper

Security trends and advances in manufacturing systems in the era of industry 4.0

2017 IEEE/ACM international conference on computer-aided design (ICCAD)

Publication Date

November 1, 2017

Author(s)

Sujit Rokka Chhetri, Nafiul Rashid, Sina Faezi, Mohammad Al Faruque

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Suggested Citation

Sujit Rokka Chhetri, Nafiul Rashid, Sina Faezi and Mohammad Abdullah Al Faruque (2017) “Security trends and advances in manufacturing systems in the era of industry 4.0”, in 2017 IEEE/ACM international conference on computer-aided design (ICCAD). IEEE, pp. 1039–1046. Available at: 10.1109/iccad.2017.8203896.

published journal article

Socioeconomic disadvantage in pregnancy and postpartum risk of cardiovascular disease

American Journal of Obstetrics and Gynecology

Publication Date

February 1, 2025

Author(s)

Kartik K. Venkatesh, Sadiya S. Khan, Janet Catov, Jiqiang Wu, Rebecca McNeil, Philip Greenland, Jun Wu, Lisa D. Levine, Lynn M. Yee, Hyagriv N. Simhan, David M. Haas, Uma M. Reddy, George Saade, Robert M. Silver, C. Noel Bairey Merz, William A. Grobman

Areas of Expertise

Safety, Public Health, & Mobility Justice

View published journal article

Abstract

Background Pregnancy is an educable and actionable life stage to address social determinants of health (SDOH) and lifelong cardiovascular disease (CVD) prevention. However, the link between a risk score that combines multiple neighborhood-level social determinants in pregnancy and the risk of long-term CVD remains to be evaluated. Objective To examine whether neighborhood-level socioeconomic disadvantage measured by the Area Deprivation Index (ADI) in early pregnancy is associated with a higher 30-year predicted risk of CVD postpartum, as measured by the Framingham Risk Score. Study Design An analysis of data from the prospective Nulliparous Pregnancy Outcomes Study-Monitoring Mothers-to-Be Heart Health Study longitudinal cohort. Participant home addresses during early pregnancy were geocoded at the Census-block level. The exposure was neighborhood-level socioeconomic disadvantage using the 2015 ADI by tertile (least deprived [T1], reference; most deprived [T3]) measured in the first trimester. Outcomes were the predicted 30-year risks of atherosclerotic cardiovascular disease (ASCVD, composite of fatal and nonfatal coronary heart disease and stroke) and total CVD (composite of ASCVD plus coronary insufficiency, angina pectoris, transient ischemic attack, intermittent claudication, and heart failure) using the Framingham Risk Score measured 2 to 7 years after delivery. These outcomes were assessed as continuous measures of absolute estimated risk in increments of 1%, and, secondarily, as categorical measures with high-risk defined as an estimated probability of CVD ≥10%. Multivariable linear regression and modified Poisson regression models adjusted for baseline age and individual-level social determinants, including health insurance, educational attainment, and household poverty. Results Among 4309 nulliparous individuals at baseline, the median age was 27 years (interquartile range [IQR]: 23–31) and the median ADI was 43 (IQR: 22–74). At 2 to 7 years postpartum (median: 3.1 years, IQR: 2.5, 3.7), the median 30-year risk of ASCVD was 2.3% (IQR: 1.5, 3.5) and of total CVD was 5.5% (IQR: 3.7, 7.9); 2.2% and 14.3% of individuals had predicted 30-year risk ≥10%, respectively. Individuals living in the highest ADI tertile had a higher predicted risk of 30-year ASCVD % (adjusted ß: 0.41; 95% confidence interval [CI]: 0.19, 0.63) compared with those in the lowest tertile; and those living in the top 2 ADI tertiles had higher absolute risks of 30-year total CVD % (T2: adj. ß: 0.37; 95% CI: 0.03, 0.72; T3: adj. ß: 0.74; 95% CI: 0.36, 1.13). Similarly, individuals living in neighborhoods in the highest ADI tertile were more likely to have a high 30-year predicted risk of ASCVD (adjusted risk ratio [aRR]: 2.21; 95% CI: 1.21, 4.02) and total CVD ≥10% (aRR: 1.35; 95% CI: 1.08, 1.69). Conclusion Neighborhood-level socioeconomic disadvantage in early pregnancy was associated with a higher estimated long-term risk of CVD postpartum. Incorporating aggregated SDOH into existing clinical workflows and future research in pregnancy could reduce disparities in maternal cardiovascular health across the lifespan, and requires further study.

Suggested Citation

Kartik K. Venkatesh, Sadiya S. Khan, Janet Catov, Jiqiang Wu, Rebecca McNeil, Philip Greenland, Jun Wu, Lisa D. Levine, Lynn M. Yee, Hyagriv N. Simhan, David M. Haas, Uma M. Reddy, George Saade, Robert M. Silver, C. Noel Bairey Merz and William A. Grobman (2025) “Socioeconomic disadvantage in pregnancy and postpartum risk of cardiovascular disease”, American Journal of Obstetrics and Gynecology, 232(2), pp. 226.e1–226.e14. Available at: 10.1016/j.ajog.2024.05.007.

published journal article

Airline schedule competition

Review of industrial organization

Publication Date

August 1, 2007

Author(s)

Jan Brueckner, Ricardo Flores-Fillol

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Suggested Citation

Jan K. Brueckner and Ricardo Flores-Fillol (2007) “Airline schedule competition”, Review of industrial organization, 30(3), pp. 161–177. Available at: 10.1007/s11151-007-9140-1.

conference paper

Ranging precision analysis of LTE signals

2017 25th european signal processing conference (EUSIPCO)

Publication Date

August 1, 2017

Author(s)

Kimia Shamaei, Joe Khalife, Zaher Kassas

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Suggested Citation

Kimia Shamaei, Joe Khalife and Zaher M. Kassas (2017) “Ranging precision analysis of LTE signals”, in 2017 25th european signal processing conference (EUSIPCO). IEEE, pp. 2719–2723. Available at: 10.23919/eusipco.2017.8081705.

published journal article

Sensor location decision model for truck flow measurement

Transportation Research Record

Publication Date

January 1, 2017

Author(s)

Kyung (Kate) Hyun, Stephen Ritchie

View published journal article

Suggested Citation

Kyung (Kate) Hyun and Stephen G. Ritchie (2017) “Sensor location decision model for truck flow measurement”, Transportation Research Record, 2644(1), pp. 1–10. Available at: 10.3141/2644-01.

MS Thesis

A Performance Assessment of the Elimination of Left-Turns at Selected Intersections

Publication Date

June 30, 2014

Author(s)

Xinyun Cao

Areas of Expertise

Infrastructure Delivery, Operations, & Resilience

View MS Thesis

Abstract

For most signalized intersections, left-turn movements are considered as a primary contributor to intersection delay. The concept of eliminating left-turn movements is now feasible with the rise of GPS-based routing which will allow the active routing of vehicles in networks with reduced left turns. This research seeks to estimate the impact of left turn reductions on overall travel time and left turn delay at intersections. The research objective is to evaluate the effect of left turn movement elimination in sample networks. The type of intersections considered is restricted to a grid network but is defined by the roadway hierarchy. A sample network was selected based on a real world network and reflecting observed volumes, travel times, and delays. The analysis approach is to eliminate left turn movements in three types of intersections by applying turn prohibitions and adjusting cycle lengths and turn penalties on other movements. Network performance is then assessed based on delay reduction, total travel time, and fuel consumption. It was concluded that selective reduction of left turn movements can improve network performance.

Suggested Citation

Xinyun Cao (2014) A Performance Assessment of the Elimination of Left-Turns at Selected Intersections. MS Thesis. UC Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/u4evf/cdi_proquest_journals_1616615092.