Roadway System Assessment Using Bluetooth-Based Automatic Vehicle Identification Travel Time Data

This monograph is an exposition of several practice-ready methodologies for automatic vehicle identification (AVI) data collection systems. This includes considerations in the physical setup of the collection system as well as the interpretation of the data. An extended discussion is provided, with examples, demonstrating data techniques for converting the raw data into more concise metrics and views. Examples of statistical before-after tests are also provided. A series of case studies were presented that focus on various real-world applications, including the impact of winter weather on freeway operations, the economic benefit of traffic signal retiming, and the estimation of origin-destination matrices from travel time data. The technology used in this report is Bluetooth MAC address matching, but the concepts are extendible to other AVI data sources

Characterizing Interstate Crash Rates Based on Traffic Congestion Using Probe Vehicle Data

Crash reduction factors are widely used by engineers for prioritizing safety investments. Work zones are routinely analyzed by the length and duration of queues. Queue detection warning technology has been growing in availability and reliability in recent years. However, there is sparse literature on the impact of freeway queueing on crash rates. This paper analyzes three years of crash data and crowdsourced probe vehicle data to classify crashes as being associated with queueing conditions or free flow conditions. In 2014, only 1.2% of the distanced-weighted hours of operation of Indiana interstates operated at or under 45 MPH. A three-year study on Indiana interstates indicates that commercial vehicles were involved in over 87% of back-of-queue fatal crashes compared to 39% of all fatal crashes during free flow conditions. A new measure of crash rate was developed to account for the presence and duration of queues: crashes per mile-hour of congestion. The congested crash rate on all Indiana interstates in 2014 was found to be 24 times greater than the uncongested crash rate. These data were also separated into both rural and urban categories. In rural areas, the congested crash rate is 23 times the uncongested crash rate. In urban areas, the congested crash rate is 21 times the uncongested crash rate. Queues are found to be present for five minutes or longer prior to approximately 90% of congestion crashes in 2014. Longer term, this information shows the importance in the development of technology that can warn motorists of traffic queues

A hazard-based analysis of airport security transit times

AbstractAirport security screening, and the amount of time it costs travelers, has been a persistent concern to travelers, airport authorities, and airlines – particularly in recent years where changes in perceived threats have resulted in changes in security procedures that have caused great uncertainty relating to security transit times. To gain a better understanding of the factors influencing travelers' security transit times, determinants of security transit times are studied by using anonymous Bluetooth media access control address matching to determine the actual security travel times of individual passengers at the Cincinnati/Northern Kentucky International Airport. These transit-time data are then analyzed using a random-parameters hazard-based duration model to statistically explore the factors that affect airport security transit times. The estimation results reveal, as expected, that a wide variety of factors affect security transit times including the number of enplaning seats (reflecting flight schedules), weather conditions, day of week, as well as obvious variables such as traveler volume and the number of open security lanes. The detailed statistical findings show that current security procedures are reactive instead of proactive, and that substantial reductions in security transit times could be attained by optimizing security operations using a statistical model such as the one estimated in this paper

Characterizing Interstate Crash Rates Based on Traffic Congestion Using Probe Vehicle Data

Crash reduction factors are widely used by engineers for prioritizing safety investments. Work zones are routinely analyzed by the length and duration of queues. Queue detection warning technology has been growing in availability and reliability in recent years. However, there is sparse literature on the impact of freeway queueing on crash rates. This paper analyzes three years of crash data and crowd-sourced probe vehicle data to classify crashes as being associated with queueing conditions or free flow conditions. In 2014, only 1.2% of the distanced-weighted hours of operation of Indiana interstates operated at or under 45 MPH. A three-year study on Indiana interstates indicates that commercial vehicles were involved in over 87% of back-of-queue fatal crashes compared to 39% of all fatal crashes during free flow conditions. A new measure of crash rate was developed to account for the presence and duration of queues: crashes per mile-hour of congestion. The congested crash rate on all Indiana interstates in 2014 was found to be 24 times greater than the uncongested crash rate. These data were also separated into both rural and urban categories. In rural areas, the congested crash rate is 23 times the uncongested crash rate. In urban areas, the congested crash rate is 21 times the uncongested crash rate. Queues are found to be present for five minutes or longer prior to approximately 90% of congestion crashes in 2014. Longer term, this information shows the importance in the development of technology that can warn motorists of traffic queues

Variable Speed Limit Study Upstream of an Indiana Work Zone with Vehicle-Matching

Managing traffic in workzones presents significant mobility and safety challenges for agencies. The goals of a workzone traffic management plan are to safely slow vehicles ahead of the workzone, maintain speeds that provide for the safety of motorists and construction workers, and manage the growth of queues. Variable speed limits have historically been presented as a technology that can dynamically regulate speed in response to prevailing traffic conditions. However, techniques used to evaluate the impact of variable speed limits typically use aggregated statistics such as mean and standard deviation to determine the “typical” speed reduction. This paper presents a new methodology to evaluate the impact of variable speed limit signage based on individual vehicle-matching. The speeds and speed changes of these matched vehicles were used to analyze individual driver response to the variable speed limits. This allows agencies to understand the impact variable speed limit signage has on the distribution of vehicle speeds. It was concluded that vehicles need to observe multiple signs prior to any tangible reduction in speed limit. Placing signs on both shoulders and in multiple longitudinal locations have a greater impact on speeds than a single sign

Travel Time Observations Using Bluetooth MAC Address Matching: A Case Study on the Rajiv Gandhi Roadway: Chennai, India

Bluetooth MAC Address matching has become a useful approach for determining travel times on corridors in the United States. In September 2013, an international collaborative study was performed using this technology along a busy urban corridor in Chennai, India. Two Purdue University graduate students traveled to Chennai, India to interact and understand the dynamics of exchanging knowledge and implementing technologies in different environments. The students worked with students from IIT Madras to determine the feasibility of Bluetooth probe vehicle technology along a typical Indian corridor. The study determined that it is feasible to expand Bluetooth use in India. Using the technology, the impact of weather, holiday and peak hour related traffic events were determined and evaluated. Of particular note were the relative high penetration of Bluetooth devices, and the exceptionally strong impact of precipitation on the heterogeneous traffic stream in Chennai, India

Performance Ranking of Arterial Corridors Using Travel Time and Travel Time Reliability Metrics

Performance measures are important for managing transportation systems and demonstrating accountability. This session presents a scalable methodology for analyzing arterial travel times, taking into account both the central tendency of the travel time and its reliability. Findings will be presented from a pilot analysis that was carried out for 28 arterials including a total of 341 signalized intersections from across the state of Indiana

Real-Time Probe Data Dashboard for Monitoring Detour Route during I-65 N Road Closure

On August 7, 2015, a 37 mile stretch of I-65 N from MM 141 to 178 was closed due to a structural evaluation of a bridge. Traffic was detoured onto US-52, SR-26, and US-231 before returning to the highway. In order to monitor delay and congestion on the detour route, a real-time dashboard was implemented in the style of the interstate Traffic Ticker. Throughout the detour, this website was used to monitor congestion in real time and measure the impact of mitigation actions. The improvement in travel can be seen from the addition of temporary signals, retiming of the US-231 corridor, and conversion of US-231 and SR-18 to a two-way stop

Leveraging High Resolution Signalized Intersection Data to Characterize Discharge Headway Distributions and Saturation Flow Rate Reliability

As highway systems become more congested, it becomes increasingly important to understand the reliability with which we can estimate important performance measures such as volume to capacity ratios, particularly as we move toward leveraging field infrastructure to obtain real-time performance measures. In 1947, Greenshields wrote a paper that characterized “green time consumed” by “car-in-line-number” that ultimately was called headway. Average headway is one of principles used by the highway capacity manual to estimate saturation flow rate at signalized intersections. However, the current analytical techniques calculate a deterministic value for saturation flow rate that does not consider the stochastic variation of saturation flow rate. This paper reviews techniques used to estimate saturation flow rate, and proposes enhanced calculation methods to group saturation flow rate estimates by queue length. Grouping saturation flow rate estimates by queue length provides a convenient framework to evaluate saturation flow rate reliability. The inter-quartile range (25% - 75%) of saturation flow rates was calculated to be 1000vph based on Greenshields’ calculation techniques. Using the proposed enhanced calculation characterizing saturation flow rate, the inter-quartile range of saturation flow rate was shown to decrease from approximately 400 vph with 5 cars in a queue to 300 vph with 10 cars in queue. Because saturation flow rate is a fundamental input to volume-to-capacity performance measures, characterizing the stochastic variation of saturation flow rates provides a basic input for assessing how reliably one can estimate important performance measures such as volume-to-capacity ratios, as well as other performance measures that build upon volume-to-capacity ratios

Identifying Effects and Applications of Fixed and Variable Speed Limits

In Indiana, distracted driving and unexpected queues have led to an increase in the amount of back-of-queue crashes, particularly on approach to work zones. This report presents new strategies for the assessment of both transportation safety and traffic operations using crowd-sourced probe vehicle data and a speed laser vehicle re-identification scheme. This report concludes by recommending strategies for the placement of variable speed limits (VSL) adjacent to work zones and suggestions for future research