by Ben Chen, PE, PTOE

Do you know where your traffic signs are?  City of Cranston in Rhode Island was surprised by the answer.  It turned out that almost 25% of the 2,600 stop signs in the city are not accounted for or authorized by the city.  The mishap caused a great deal of legal troubles.  Read the full story in the New York Times:

  http://www.nytimes.com/2010/11/30/us/30stop.html

One alternative “seeks to obviate the difficulties of the junction of four or more roads by a gyratory system of regulating traffic…”, or what is referred to as a roundabout. But Olmsted concludes that a roundabout would work well only at light traffic intersections and with little or no police control “provided the drivers could possibly be induced to turn out of their direct way in order to gyrate without being compelled to do so by the police.” 

But at heavy traffic intersections, “it would seem clear that the prompt and orderly regulation of which vehicle is to give way for the other cannot possibly be effected under such conditions, even by a large number of policemen, as well as can be done single-handed on the ordinary crossing.”

In other words, “the best crossing is a four-way crossing nearly at right angles.”

In 1910, there were 458,500 registered vehicles in the United States.  In 2010, there are 246,000,000 cars on US roads. 

We wonder what Olmsted would say about this “Magic Roundabout” in Swindon, England.  Built in 1972, it has five “mini-roundabouts”  arranged in a circle.  In 2009 it was voted the fourth scariest junction in Britain:

The 2-minute video below shows two examples of how easy the Dashboard Module is to use.  The hybrid ArcGIS Server/Google map makes locating a point quick and informative.

View a live example of the Dashboard Module created for the Southern California Association of Governments (SCAG).

In the transportation field, a similar effort occurs with traffic signal retimings / optimizations.  The traffic signal retiming process involves collecting current traffic volumes and properly allocating green time to the various signal phases.  While most road agencies have programs to keep their traffic counts current, the subsequent retiming of traffic signals to reflect those current traffic volumes is an effort that is sorely lacking.

In fact, the National Transportation Operations Coalition gave the nation a D for overall traffic signal operations in the most recent National Traffic Signal Report Card (2007).  A primary reason for the poor grade was cited as outdated traffic signal timings.  Traffic signal timings are recommended to be reviewed at least every three years.  The reality is that many traffic signals can go several years, even decades between timing changes. The Report Card report estimates that these outdated traffic signal timings account for approximately 5 to 10 percent of all traffic delay or 295 million vehicle-hours of delay each year on major roadways alone.  With the benefits outweighing the costs by an estimated 40:1 or more, additional investments should be made into traffic signal retiming / optimization projects. 

So let the Census serve as a reminder to retime those traffic signals, just don’t wait until the 2020 Census before retiming them again.

Traffic engineers/planners and law enforcement officials primarily identify intersection related crashes through a pre-established distance from the center of the intersection and/or an officer’s selection of the crash being “intersection related” on the actual crash report.  Utilizing these criteria, network-wide analyses are then performed to identify the intersections with the highest crashes, crash severity, crash rate, etc.

But is this really an “apples to apples” analysis or are there some oranges in there?

Roadway intersections can have very different characteristics and attributes.  Items such as alignment, geometrics, traffic volumes, and speed limits can vary greatly when looking at intersections throughout an agency’s road network.  A recent article in the Institute of Transportation Engineers (ITE) Journal(1) examines this issue and explores a methodology to more accurately identify intersection related crashes.

The article states that the default distances used by many state agencies range anywhere from 50 feet to upwards of 500 feet to determine if a crash is considered related to the intersection.  Other agencies utilize items such as vehicle movements, collision type, and the “intersection related” crash report selection as the criteria to identify intersection related crashes.

The authors go on to discuss a detailed analysis that was performed on over 13,000 crash reports in the state of Florida.  They discovered crash reports that should have been coded as intersection related (~ 15%) and examined possible relationships between intersection attributes and distances from the intersection to still consider a crash as intersection related.

I would like to say that the article concludes with some sort of cookie cutter parameters that can be applied to various intersections types.  The fact is that the variability in crash data from the initial crash report to the subsequent analysis will never be able to provide standards that can be applied in all cases.  However, the article brings to mind that it is important to recognize that there can be significant differences in intersections and, therefore, prudent to analyze similar intersections rather than intersections as a whole to actually conduct more of an “apples to apples” comparison.

(1) Abdel-Aty, M., Wang, X., and Santos, J. “Identifying Intersection-Related Traffic Crashes for Accurate Safety Representation.” ITE Journal, Dec 2009.

Lieutenant David Livingston demonstrates TCAT 2.0 to law enforcement officers at the Troy Police Department on Wednesday

Law Enforcement and Traffic Engineering Officials Receive Training on a Web-Based Crash Analysis Program

WATERFORD–In a continued effort to reduce traffic crashes in the state of Michigan, the Traffic Improvement Association (TIA) hosted a training session for the users of its newest Traffic Crash Analysis Tool (TCAT 2.0) on Monday.  The four-hour training session, which was held at the Oakland County Executive Office Building in Waterford, was designed to teach law enforcement and traffic engineering officials the capabilities of the new program. 

“Since 1967, TIA has made the availability of accurate and timely traffic crash data a high priority,” said Susan M. Cischke, group vice president of Sustainability, Environment, and Safety Engineering at Ford Motor Company, and chair of the TIA Board of Directors.  “With the advancement of computerized technology, TIA has made significant progress.”

TCAT 2.0 is a comprehensive web-based traffic crash analysis program that was designed for the detailed study of traffic crashes at any location within the state of Michigan. The program receives a weekly update of data from the Michigan State Police, which guarantees that TCAT 2.0 users are able to analyze the most up-to-date crash data. 

“TCAT 2.0 provides increased speed, better accuracy, and a number of additional features that enhances the user’s ability to promote traffic safety in Michigan,” said James A. Santilli, Jr., coordinator of Information Technology, Public Relations, and Traffic Safety Services at TIA. 

Santilli, who serves as the project manager for TCAT 2.0, stated the program is coordinated and funded by TIA, and the computer programming duties are conducted by Midwestern Software Solutions (MS2).  MS2, which is based in Ann Arbor, developed TCAT 2.0 based on the expert advice of TIA’s traffic engineers and the Road Commission for Oakland County (RCOC). 

“Currently, MS2 has clients ranging from Los Angeles to New York,” said Santilli.  “As a result, TIA was confident that MS2 had the knowledge and experience needed to take TCAT to the next level.” 

TCAT 2.0 has the ability to search various types of locations for specific data, view crash statistics for several categories, interact with a map to obtain detailed crash statistics and other information pertaining to a location, view collision diagrams, review UD-10 crash report images, and create intersection and road segment ranking reports for a comparative analysis. 

“Thanks to TIA, we know where the crashes are occurring and frequently what caused them,” said Brent O. Bair, managing director of RCOC.  “This data allows us to select and design projects that will have the greatest likelihood of reducing traffic fatalities and serious injuries.” 

According to Santilli, Michigan State Police records indicate there were 980 persons killed and 74,568 persons injured in 316,057 reported motor vehicle traffic crashes in Michigan during 2008.  “On average, one person was killed every 8 hours and 56 minutes, and one person was injured every 7 minutes and 3 seconds,” said Santilli. 

In 2008, Oakland County had 0.43 deaths per 100 million vehicle miles of travel, which is less than half the statewide rate of 0.97 deaths per 100 million vehicle miles of travel. 

“This is not an overnight phenomenon,” observed Bair.  “This was more than 40 years in the making, and represents the collective efforts of a lot of people, from RCOC to TIA, to local law enforcement and others.” 

Bair also acknowledges the state legislature, which mandated seatbelt usage, and the auto manufacturers that have continuously improved the safety of their vehicles. 

Currently, there are more than one-hundred users of TCAT 2.0, and TIA continues to add users daily.  User access is restricted to government agencies and private traffic engineering firms. 

“Having a system to assemble traffic crash data for problem identification and site selection is critical for initiating an effective enforcement and prevention mobilization,” said Oakland County Sheriff Michael J. Bouchard.  “Through the use of TCAT 2.0, law enforcement agencies can target the problem locations in an effort to reduce fatalities and serious injuries.” 

More than fifty representatives were present from the following agencies on Monday: Auburn Hills Police Department; Battle Creek Department of Public Works; Bergmann Associates; Clawson Police Department; The Corradino Group; Farmington Hills Department of Engineering; HNTB Michigan, Inc.; Hubbell, Roth & Clark, Inc.; Keego Harbor Police Department; Lake Orion Police Department; Livonia Police Department; Madison Heights Community Development; Michigan Department of Transportation; Oak Park Department of Public Safety; Oakland County Sheriff’s Office; Road Commission for Oakland County; Rochester Department of Public Works; Rochester Hills Department of Public Works; Southeast Michigan Council of Governments; Southfield Police Department; Traffic Improvement Association; Troy Engineering Department; Troy Police Department; URS Corporation; Wade Trim; West Bloomfield Police Department; and Wixom Police Department. 

About TIA 

TIA is a non-profit traffic safety organization that currently serves approximately seventy communities in Oakland, Macomb, Wayne, and Livingston Counties.  TIA was organized in 1967 by community leaders to address adverse traffic safety issues in Oakland County.  Today, Oakland County has one of the lowest traffic crash fatality rates in the nation, and TIA was instrumental in this achievement.  The mission of TIA is to facilitate engineering, education, and enforcement programs that reduce human and economic losses caused by traffic crashes, and improve mobility in Michigan.