Policy

Explaining the “Immigrant Effect” on Auto Use: The Influences of Neighborhoods and Preferences

Chatman, Daniel G.
2014

Since immigrants will account for most urban growth in the United States for the foreseeable future, better understanding their travel patterns is a critical task for transportation and land use planners. Immigrants initially travel in personal vehicles far less than the US-born, even when controlling for demographics, but their reliance on autos increases the longer they live in the US. Cultural or habitual differences, followed by assimilation to auto use, could partly explain this pattern; and it may also be partly due to changes in locations and characteristics of home and work...

Equity in Congestion-priced Parking: A Study of SFpark, 2011 to 2013

Chatman, Daniel G.
Manville, Michael
2018

Cities could reduce or eliminate cruising for parking by correctly setting parking meter rates, but would doing so harm lower-income drivers? We examined the question using data on more than 17,000 parked vehicles and their drivers from SFpark, a federally funded market-priced parking experiment in San Francisco. But we found that lower-income parkers are more likely to use street parking and meter rates had small effects on usage. Raising prices did not increase sorting across blocks by income. Controlled analysis yielded mixed and weak evidence that lower-income parkers may be less...

A Wireless Token Ring Protocol for Intelligent Transportation Systems

Lee, D.
Attias, R.
Puri, A.
Sengupta, R.
Tripakis, S.
Varaiya, P.
2001

The wireless token ring protocol (WTRP) is a medium access control (MAC) protocol for wireless networks in intelligent transportation systems (ITS). It supports quality of service (QoS) in terms of bounded latency and reserved bandwidth. The WTRP is efficient in the sense that it reduces the number of re-transmissions due to collisions. It is fair in the sense that each station takes a turn to transmit and is forced to give up the right to transmit after transmitting for a specified amount of time. It is a distributed protocol that supports many topologies since not all stations need to be...

Decentralized Error-Dependent Transmission Control for Model-Based Estimation Over a Multi-Access Network

Huang, Ching-Ling
Sengupta, Raja
2008

This paper is motivated by the estimation problem and active safety design for ITS. We investigate the performance of model-based estimation over a multi-access network and emphasizes on asymptotic time-averaged MSE while using error-dependent transmission control. The performance of this decentralized policy is analyzed and an improved policy is also proposed to achieve robustness in a shared channel. Our results suggest that, while designing communication logic for vehicular safety applications, dynamics of the system and channel congestion should be considered at the same time.

Quantified Traveler: Travel Feedback Meets the Cloud to Change Behavior

Sengupta, Raja
Walker, Joan L.
2015

Halting climate change will require a concerted effort to reduce emissions from on-road vehicles. While significant progress has been made to improve vehicle efficiency and reduce CO 2 emissions, surface transportation accounted for half the increase in US green-house gas (GHG) emissions over the past two decades. Today, surface transportation accounts for 24 percent of all US emissions. Automobile improvements alone will not be sufficient to meet federal and state emissions targets; policy makers also need to identify solutions that reduce the demand for car travel. Information technology...

Real-time Estimation of a Markov Process Over a Noisy Digital Communication Channel

Xu, Qing
Sengupta, Raja
2011

We study the real-time estimation of a Markov process over a memoryless noisy digital communication channel. The goal of system design is to minimize the mean squared estimation error. We first show the optimal encoder and decoder can be memoryless in terms of the source symbols. We then prove the optimal encoder separates the real space with hyperplanes. In the case of the binary symmetric channel and scalar source, the optimal encoder can be a threshold. A recursive algorithm is given to jointly find a locally optimal encoder and decoder for the binary symmetric channel. For a memoryless...

Scaling Laws for Cooperative Node Localization in Non-Line-of-Sight Wireless Networks

Ekambaram, Venkatesan
Ramchandran, Kannan
Sengupta, Raja
2011

We study the problem of cooperative node localization in non-line- of-sight (NLOS) wireless networks and address design questions such as, "How many anchors and what fraction of line-of-sight (LOS) measurements are needed to achieve a specified target accuracy?". We analytically characterize the performance improvement in localization accuracy as a function of the number of nodes in the network and the fraction of LOS measurements. In particular, we show that the Cramer- Rao Lower Bound (CRLB) can be expressed as a product of two factors - a scalar function that depends only on the...

Stability Bounds on Entropy Rate for Real-Time Tracking an Unstable LTI Process Over a Multi-Access Network

Huang, Ching-Ling
Sengupta, Raja
2009

We assume the separation of source/channel coding and propose a framework for real-time tracking an unstable, scalar, linear time-invariant (LTI) process via a G/G/1- queueing network. We derive a stability bound on the entropy rate of an unstable LTI process such that tracking error can stay bounded for specified moment. This bound is a function of the moment to be stabilized, encoder efficiency, quantization accuracy, and network parameters. This bound is sufficient under all load conditions and tight when the network is heavily utilized. Proposed framework covers a broad class of...

Stability of Dynamic Traveling Repairman Problem Under Polling-Sequencing Policies

Huang, Jiangchuan
Sengupta, Raja
2013

We establish a necessary and sufficient condition for stability in the dynamic traveling repairman problem (DTRP) [3] under the class of polling-sequencing (P-S) policies satisfying unlimited-polling and economy of scale. The P-S class includes some of the policies proven to be optimal for the expectation of system time under light and heavy loads in the DTRP literature. The number of tasks inside each polling partition is shown to be a Markov chain. Policies such as first come first serve, traveling salesman policy, nearest neighbor and Daganzo's algorithm are shown to have economy of...

System Time Distribution of Dynamic Traveling Repairman Problem Under the PART-n-TSP Policy

Huang, Jiangchuan
Sengupta, Raja
2015

We propose the PART-n-TSP policy for the Dynamic Traveling Repairman Problem [1]. We compute a good approximation for the distribution of the system time, defined as the elapsed time between the arrival and the completion of each task. PART-n-TSP stabilizes the system for every load in [0; 1). PART-n-TSP has lower system time variance than PARTTSP [14] and Nearest Neighbor [1] when the load is neither too small or too large. We show that PART-n-TSP is also optimal for system time expectation under light and heavy loads.