Bus Transit Operational Efficiency Resulting from Passenger Boardings at Park-and-Ride Facilities

In order to save time and money by not driving to an ultimate destination, some urban commuters drive themselves a few miles to specially designated parking lots built for transit customers and located where trains or buses stop. The focus of this paper is the effect Park-and-Ride (P&R) lots have on the efficiency of bus transit as measured in five bus transit systems in the western U.S. This study describes a series of probes with models and data to find objective P&R influence measures that, when combined with other readily-available data, permit a quantitative assessment of the significance of P&R on transit efficiency. The authors developed and describe techniques that examine P&R as an influence on transit boardings at bus stops and on bus boardings along an entire route. The regression results reported are based on the two in-depth case studies for which sufficient data were obtained to examine (using econometric techniques) the effects of park-and-ride availability on bus transit productivity. Both Ordinary Least Square (OLS) regression and Poisson regression are employed. The results from the case studies suggest that availability of parking near bus stops is a stronger influence on transit ridership than residential housing near bus stops. Results also suggest that expanding parking facilities near suburban park-and-ride lots increases the productivity of bus operations as measured by ridership per service hour. The authors also illustrate that reasonable daily parking charges (compared to the cost of driving to much more expensive parking downtown) would provide sufficient capital to build and operate new P&R capacity without subsidy from other revenue sources

Thermodynamic Analysis of Interacting Nucleic Acid Strands

Motivated by the analysis of natural and engineered DNA and RNA systems, we present the first algorithm for calculating the partition function of an unpseudoknotted complex of multiple interacting nucleic acid strands. This dynamic program is based on a rigorous extension of secondary structure models to the multistranded case, addressing representation and distinguishability issues that do not arise for single-stranded structures. We then derive the form of the partition function for a fixed volume containing a dilute solution of nucleic acid complexes. This expression can be evaluated explicitly for small numbers of strands, allowing the calculation of the equilibrium population distribution for each species of complex. Alternatively, for large systems (e.g., a test tube), we show that the unique complex concentrations corresponding to thermodynamic equilibrium can be obtained by solving a convex programming problem. Partition function and concentration information can then be used to calculate equilibrium base-pairing observables. The underlying physics and mathematical formulation of these problems lead to an interesting blend of approaches, including ideas from graph theory, group theory, dynamic programming, combinatorics, convex optimization, and Lagrange duality

Existence and Minimax Theorems for Adversarial Surrogate Risks in Binary Classification

Adversarial training is one of the most popular methods for training methods robust to adversarial attacks, however, it is not well-understood from a theoretical perspective. We prove and existence, regularity, and minimax theorems for adversarial surrogate risks. Our results explain some empirical observations on adversarial robustness from prior work and suggest new directions in algorithm development. Furthermore, our results extend previously known existence and minimax theorems for the adversarial classification risk to surrogate risks.Comment: 37 page

Steps to Supplement Park-and-Ride Public Transit Access with Ride-and-Ride Shuttles

Public transit ridership in California declined in the five years before the pandemic of 2020–21 and dropped significantly further after the pandemic began. A sharp downward step in the level of transit boarding occurred after February 2020, and continues to the date of this report as a result of the public-health guidance on social distancing, expanded work-at-home, and a travel mode shift from public transit to private cars. A critical issue has come to the foreground of public transportation policy, namely, how to increase the quality and geographic reach of transit service to better serve the essential trips of mobility disadvantaged citizens who do not have access to private vehicle travel. The research focus of this report is an examination of the circumstances where fixed route bus route service could cost-effectively be replaced by on-demand microtransit, with equivalent overall zone-level efficiency and a higher quality of complete trip service. Research methods were reviews of documented agency experience, execution of simple simulations, and sketch-level analysis of 2019 performance reported in the National Transit Database. Available evidence is encouraging and suggestive, but not conclusive. The research found that substitutions of flexible microtransit for fixed route buses are already being piloted across the U.S., with promising performance results. The findings imply that action steps could be taken in California to expand and refine an emphasis on general purpose microtransit in corridors and zones with a relatively high fraction of potential travelers who are mobility disadvantaged, and where traditional bus routes are capturing fewer than 15 boardings per vehicle hour. To be sufficiently productive as fixed route replacements, microtransit service technologies in the same or larger zones need to be capable of achieving vehicle boardings of five per hour, a challenge worth addressing with technology applications. Delivery of microtransit service can be undertaken through contracts with a growing set of private sector firms, which are developing processes to merge general purpose customers with those now assigned to ADA-required paratransit and Medi-Cal-supported non-emergency medical transport

Impact of park-and-ride on public transit ridership

We examine the relative impact of increased housing vs. increased parking availability on ridership of public transit. The approach sheds light on the trade-off in alternative land uses near transit stops: Park-and-ride (PnR) vs. transit-oriented development (TOD). In the example of one city studied here, econometric analysis suggests that PnR provides more transit ridership than housing. However, the transit agency may choose the alternative of reducing PnR and partnering with housing developers as a source of new non-fare revenue that creates vibrant, walkable growth in station areas, which is considered to be just as important as ridership

Stability of elastically supported columns

A criterion is developed for the stiffness required of elastic lateral supports at the ends of a compression member to provide stability. A method based on this criterion is then developed for checking the stability of a continuous beam-column. A related method is also developed for checking the stability of a member of a pin-jointed truss against rotation in the plane of the truss