Traffic Engineering

Friday Seminar - Vikash Gayah on The Aggregate Effect of Turns on Urban Traffic Networks

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overland ave traffic

This week’s Friday TRANSOC Seminar has Vikash Gayah, Ph.D. candidate, University of California, Berkeley, presenting “The Aggregate Effect of Turns on Urban Traffic Networks.” 

This research creates and uses macroscopic traffic models to describe the aggregate behavior of vehicles on urban street networks. Insights gained from these models can then be used to design network-wide policies that may increase the ability of these networks to serve vehicle-trips. In particular, this work focuses on the turning maneuvers that exist in networks with multiple routes. The presence of multiple routes and turning maneuvers are found to have two effects on aggregate vehicle behavior: 1) they cause unstable and inefficient behavior when a network is congested; and, 2) they may reduce maximum vehicle flows across the network. Fortunately, this work finds that limiting the rate at which vehicles are allowed to enter a network and providing drivers with real-time information on current traffic conditions can help mitigate the first effect and allow the network to operate more efficiently. It is also found that the second effect may not always be harmful—lower network flows do not necessarily result in decreased network efficiency if the lower flows are accompanied by more direct vehicle routing. In fact, two-way networks, which accommodate conflicting left-turns and result in lower maximum vehicle flows than one-way networks, are found to serve trips at a higher rate because drivers travel shorter distances on average. Thus, in many cities, maximum network efficiency can be improved by converting one-way streets to two-way operation.

The seminar will take place at 4:00 PM in534 Davis Hall. Please join us for a TRANSOC-sponsored Cookie Hour in the ITS Library at 3:30 PM.

Friday Seminar - Lily Elefteriadou on Driver Behavior and Characteristics and Their Use in Traffic Modeling

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Driver Experience @ Limeira

This week's Friday TRANSOC Seminar has Lily Elefteriadou, Professor and Director of the Transportation Research Center, School for Sustainable Infrastructure and the Environment, University of Florida, presenting “Driver Behavior and Characteristics and Their Use in Traffic Modeling.” 

Traffic modeling has frequently considered and accounted for variability in driver behavior and characteristics.  For example, microscopic traffic simulators have the capability to replicate vehicular movements (such as lane changing) considering driver characteristics to a significant level of detail.  Such traffic simulators can typically replicate traffic streams with several different driver types which are based on driver aggressiveness.  Vehicular movements (such as car following) are then determined based on the respective action of the particular driver type.  However, a limited amount of research has been reported to categorize driver types or to link particular driving actions with a set of driver types and their characteristics.  Car-following, lane changing, and gap acceptance algorithms have rarely been calibrated to match various driver types, and it is not always clear how micro-simulators incorporate driver behavior aspects into these algorithms.  This presentation will describe two approaches to collecting driver behavior and characteristics-related data so that they can be used to improve traffic micro-simulators.  The first approach is based on focus groups, while the second is based on in-vehicle field data collection with an instrumented vehicle.  The presentation will describe these two data collection approaches and will provide three example applications related to freeway merging, car-following, and arterial lane changing. 

Friday Seminar - Tasos Kouvelas on Adaptive Fine-tuning for Large-scale Nonlinear Traffic Control Systems

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Traffic Light Tree

This week’s Friday TRANSOC Seminar has Tasos Kouvelas, Ph.D., Postdoctoral Researcher, University of California, Berkeley, presenting  “Adaptive Fine-tuning for Large-scale Nonlinear Traffic Control Systems.”

This talk introduces and analyzes a new learning/adaptive algorithm that enables automatic fine-tuning of Large-scale Nonlinear Traffic Control Systems (LNTCS), so as to reach the maximum performance that is achievable with the utilized control strategy. LNTCS have many applications in transportation, as with urban signal control or ramp metering, and yet their efficient design and deployment remains elusive due to the involved complexity and nonlinearities. Often, the deployment of a new algorithm (or the updating of an existing one) requires extensive fine-tuning before it reaches its best achievable performance. Typically, this fine-tuning procedure is conducted manually, via trial-and-error, relying on expertise and human judgment and without the use of a systematic approach. The proposed Adaptive Fine Tuning (AFT) algorithm is aiming at replacing the conventional manual optimization practice with a fully automated online procedure. The talk provides a detailed analysis of the algorithm as well as a step-by-step application description. Finally, application results of the algorithm to real-time fine-tuning problems of general LNTCS are presented using the commercial micro-simulation tool AIMSUN.

The seminar will take place today 4:00 PM in 406 Davis Hall. Please join us for a TRANSOC-sponsored Cookie Hour in the ITS Library at 3:30 PM.

Friday Seminar - Nikolas Geroliminis on Traffic Systems

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A (small) part of traffic-1

Today’s TRANSOC Friday Seminar has Nikolas Geroliminis, PhD., Assistant Professor, Urban Transport Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL) presenting “The M6 of traffic systems: Macroscopic Modeling, Monitoring and Management of Multimodal Mobility.”

As more people and transport modes compete for limited urban space to travel, there is a need to understand how this space is used for transportation and how it can be managed to avoid traffic congestion. Our research seeks to shed some light in the modeling, planning and management of traffic flow for overcrowded cities with multimodal transport. We develop methodologies to model and understand the collective behavior for different types of multi‐modal systems, with emphasis in conflicts for the same road space (e.g. mixed traffic of buses and cars). The goal is to develop optimization tools on how to distribute city road space to multiple modes and to understand the level of accessibility for cities of different structures. We also investigate what type of real-time active traffic management schemes (congestion pricing, vehicle restriction, large scale traffic signal control) can improve mobility measures in a city. Until now traffic control systems in urban areas are locally programmed with little control over the impact of a micro-scale response to the macro-scale level. We build a hierarchical feedback control network of multiple levels. The validation of the modeling methodologies and the traffic management schemes are conducted in various and complex city structures scenarios using data from field experiments advanced micro-simulations.

The seminar will take place today 4:00 PM in 406 Davis Hall. Please join us for a TRANSOC-sponsored Cookie Hour in the ITS Library at 3:30 PM.

Automated Enforcement: Safety or Revenue?

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703px-Red-light-camera-springfield-ohio

Red light cameras and other forms of automated traffic law enforcement continue to generate controversy. This week, Iowa Governor Terry Branstad said that he is in favor of banning such devices and a bill was introduced in the Colorado legislature to ban photo enforcement. On the other hand, the Insurance Institute for Highway Safety found strong public support for camera enforcement in cities with such programs. Much of the debate in Iowa and elsewhere stems from disagreement over whether such enforcement enhances traffic safety or merely produces revenue in the form of fines. Privacy is also a big concern and some who object on these grounds also see a very disturbing trend towards privatization of law enforcement. US PIRG released a report in October which outlines some of the pitfalls in privatization, including conflicts of interest, political clout of vendors and possible intrusion in setting transportation policy.

How much longer do we have to wait for cars that drive themselves?

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Google Self-Driving Car

Today Greater Greater Washington blogged about the prospect of self-driving cars.

Whether we are prepared for it or not, the next revolution in transportation will be here soon, and it won't be streetcars, monorails, segways, or electric vehicles. It will be self-driving cars, and the adoption of this technology will change everything we accept as a given in the field of transportation planning.

They also link to a Washingtonian interview with Michael Pack, director of the CATT Laboratory at the University of Maryland, and noted transportation technologist. He sees autonomous vehicles as a potential solution for congestion, "Completely automated cars that take the driver out of the equation, communicate with one another, and can travel at high speeds within six inches of one another."

Will Hansfield on Greater Greater Washington projects that we might see self driving cars commercialy viable in the US in the next 7-12 years. Given the clip of research, it might not be far off. Looking at "intelligent vehicles" research in TRID, automation is trend that has been becoming more common over the years. From cyber cars to intercontinental van journeys, integrated systems for autonomous vehicles are coming.

The PATH program from ITS Berkeley has been looking at autonomous vehicles for quite a while now. Though the most famous driverless cars might be the new fleet from Google. Sorry KITT.

Friday Seminar - Ilgin Guler on Strategies for Sharing Bottleneck Capacity among Buses and Cars

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let photo speak...

Tomorrow's TRANSOC Friday Seminar features Ph.D. candidate Ilgin Guler presenting, "Strategies for Sharing Bottleneck Capacity among Buses and Cars."

Buses that operate in mixed traffic can be impeded by car congestion, leading to unreliable and slow bus service. Conversely, buses that frequently stop to serve passengers can interfere with the movement of cars. To address these issues, exclusive bus lanes have often been used to segregate buses from other traffic. These exclusive bus lanes provide a means for buses to bypass car queues, thereby increasing bus speed and potentially decreasing the total person hours travelled on a network. In urban settings exclusive bus lanes are typically deployed by converting an existing general purpose lane to bus use only. However, in cases where bus flow is low, these lane conversions can increase the queuing and delays to cars. The problem is particularly acute at roadways bottlenecks, since cars now discharge from one less lane, even when the bus lane is unoccupied.

This research examines strategies for judiciously inserting cars between buses in ways that minimize the losses in a bottleneck’s car carrying capacity when bus demand is low. The idea entails sharing lanes among buses and cars in the vicinities of critical bottlenecks; and to have these shared lanes augment exclusive bus lanes that are deployed elsewhere throughout the network. The specific type of sharing strategy to be used near any given bottleneck would depend upon its operating conditions. In all cases the goal is to prioritize bus travel while minimizing the additional delays that this prioritization imparts to cars. Analysis unveils the ranges of bus demands for which the shared‑lane strategies are superior to ordinary lane conversions. We find that the shared-lane strategies have merit in many instances. Implementing these strategies for a real-world case study in Amman, Jordan produces promising outcomes: simulation analysis indicates that the delay savings to cars brought by the lane–sharing strategies are considerable. The proposed ideas can help increase the political acceptability of bus priority systems and promote public transportation in cities of various sizes.

The Seminar will be from 4-5pm in 406 Davis Hall. There will be no cookie hour precedding it this week, so you'll need to sort out your sugar fix some other way. 

Friday Seminar - Rabi G. Mishalani on Schedule Based Transit Operations

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This Friday's TRANSOC Seminar features

Rabi G. Mishalani, Ph.D., Associate Professor, Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, presenting on "Analysis and Quantification of the Effects of Schedule-Based Transit Operations Control on Service Reliability."

The effects of bus drivers' reactions to schedules, given the status of the buses they are operating, on service reliability are investigated and quantified analytically and empirically. The hypothesis that drivers may deliberately, as a form of control, lengthen or shorten dwell times at stops or adjust speeds between consecutive stops depending on whether buses are ahead or behind schedule is examined. An analytical relationship is derived, based on which an empirical study is conducted. The relationship describes the progression of reliability from stop to stop as a function of drivers' possible reactions to the schedule in the presence of exogenous factors. Such reactions are explored in an empirical study using a large Automatic Vehicle Location (AVL) data set collected by The Ohio State University's Campus Transit Lab (CTL). The drivers' reactions to the schedule are found to be helpful in improving service reliability. Moreover, the magnitudes of the improvements in reliability, resulting from such reactions, and the deterioration of reliability, due to exogenous factors, are quantified. Given the reliance on CTL data in conducting this study, a brief motivation, history, description, and uses of CTL are discussed as well.

Rabi Mishalani is an associate professor at The Ohio State University with the Department of Civil and Environmental Engineering and Geodetic Science. His areas of interest and expertise include the application of probability modeling and statistical methods to the planning and managing of public transportation and transportation infrastructure systems. He is playing a lead role in developing and directing OSU's Campus Transit Lab (CTL), a "living lab" that supports research, education, and outreach. He also is the co-director of the US DOT Region V University Transportation Center.

The seminar is Friday, November 4, 4-5pm, 406 Davis Hall.

Ampelmännchen turns 50.

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Berlin 2007: Ampelmann

50 years ago today, the most iconic traffic light for pedestrian crossings debuted in German Democratic Republic - Ampelmännchen or "Little Traffic Light Man." On this day in 1961, traffic psychologist Karl Peglau introduced the novel design to improve predestrian safety: 

 

In several studies, he concluded that many of the 10,000 traffic deaths between 1955 and 1960 could be attributed to one thing: Pedestrians had to follow the same traffic lights as cars. When it was foggy, the red-yellow-green lights did not offer sufficient orientation for visually impaired pedestrians. According to Peglau, they provided the opposite, and were a safety risk. He estimated the economic damages of this problem in the GDR reached up to 155 million deutsche marks in 1959.

"Clearly distinguishable guiding signals" were meant to address this. A friendly red man with thick, outstretched arms would prompt pedestrians to stop, and a lively green man in mid-stride would denote the appropriate time to walk. Peglau provided personal characteristics in order to "appropriately provoke the desired pedestrian behavior through emotion," giving them pug noses, fingers, ears and mouths.

 

After the Reunification of German, the iconic Ampelmännchen was quickly introduced to West Berlin and continues to be a symbol of the unified city. 

Friday Seminar - Weihua Gu on Capacity Models for Curbside Bus Stops

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LACMTA

Tomorrow's TRANSOC Friday Seminar features Ph.D. candidate Weihua Gu presenting, "Capacity Models for Curbside Bus Stops with Multiple Berths."

When multiple bus lines merge at a busy, multi-berth bus-stop in a congested city, long bus queues might occur due to an inadequate number of berths.  Disruptive bus overtaking maneuvers and chaotic passenger boarding processes may therefore ensue at the stop.  To unveil the cause-and-effect relations behind this congestion, models are developed to predict the bus-carrying capacity for curbside bus-stops.  These capacities are functions of the stop’s number of bus berths, and other key operating factors.  An analytical solution is derived for a queueing model that describes the unique operating features of serial bus berths.  The results from these models show that conventional wisdom in this field is incomplete and incorrect in many instances.  The proposed models can provide practitioners better guidelines for choosing the number of berths to achieve a desired capacity at a curbside bus-stop.  The models also give insights to improve ways of operating the stop.  These ways include, but are not limited to, allowing or prohibiting bus overtaking maneuvers under certain circumstances, and strategies to manage passenger boarding and alighting processes.  Further, these bus-stop models can be applied to other serial queueing systems in the transportation field, including taxi queues, Personal Rapid Transit systems, and toll plazas with tandem booths.

The seminar will take place from 4-5 pm in 406 Davis on October 14. Please come to TRANSOC's Cookie Hour preceeding the seminar at 3:30 pm in the library. 

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