Good Practice Traveler Information - Houston and Chicago

Houston

Posted travel times proved important to drivers in the Houston, TX metropolitan area, who emailed Houston TransStar – the partnership responsible for coordinating the planning, design, and operation of Houston's roadways, emergency management functions, and intelligent transportation systems (ITS) – requesting that more useful information be posted on blank DMSs.

Since the mid-1990s, Texas Department of Transportation (TxDOT) staff at Houston TranStar had been posting travel times during peak periods on DMSs; however, many of the agency's signs remained blank during offpeak times. In an effort to sue the signs more efficiently, TransStar initiated a campaign to post on the signs a safety message of the week. But through emails to the Houston TansStar Web site, the agency learned that motorists felt that the weekly safety messages were not the best use of the signs.

TxDOT and the Texas Transportation Institute then conducted a Web survey asking what types of messages motorists desired. The survey indicated that drivers were primarily interested in seeing incident information (93 percent) and travel times (82 percent). Many respondents indicated that although incident information is important, they also need travel time information to better determine how incidents affect their travel. Real-time travel time information posted on DMS influenced drivers' route choice. Eighty-five percent of respondents indicated that they changed their route based on the information provided (of this 85 percent, 66 percent said that they saved travel time as a result of the route change).

Responding to motorist feedback TransStar created an automated system that post travel times on up to 100 DMSs at 10-mintue intervals across more that 344 centerline miles of Houston-area freeways. Travel times are based on data collected from nearly 2 million EZ TAG toll transponders currently circulating in the Houston metropolitan areas. Data from these vehicle probes are collected at 232 locations and transmitted to TransStar for analysis. Reader stations are, on average, 2 to 3 miles apart, but not more than 5 miles apart.

Chicago

The Illinois State Toll Highway Authority (ISTHA) covers a significant part of northeastern Illinois, the third most congested area in the country. ISTHA provides average travel times from toll plaza to toll plaza based on "I-PASS" toll transponder data collected by its electronic toll collection system. Users of the automated I-PASS toll collection system now exceed 1.5 million, providing ISTHA with a significant penetration of vehicle probes that offer high-quality, time-stamped location information in near real-time.

ISTHA uses data from three sources to calculate travel times: I-PASS transponders, radar sensor stations along tolled roads, and loop detectors maintained by the Illinois Department of Transportation. ISTHA currently posts travel times on 33 DMS located on tolled and nearby non-tolled roads. Although ISTHA has not conducted a formal study, emails and calls to the customer input line indicate that drivers approve of travel time availability information, and will complain when a non-incident-related message is posted during times when travel time information is normally available.