Analysis of Major Freeway Incidents in Houston, Texas

Abstract

An analysis of major freeway incidents in Houston, Texas, was conducted. The data base analyzed was provided by the Houston Police Department solo motorcycle patrol division. This division responds to all freeway lane-blocking incidents that are expected to last more than approximately 45 minutes. Over a 7-year period between 1986 and 1992, the division documented the details of 612 major freeway incidents to which it responded. From these data, it was estimated that major freeway incidents occur in Houston at a rate of 0.68 incident per 100 million vehicle-kilometers (MVK). That is equivalent to a major incident every 147 MVK. Major incidents were nearly 3.5 times as likely to occur within the interchanges (based on vehicle-kilometers driven) as between them. Of the 612 major incidents included in the data base, 498 (81.5 percent) involved trucks only (even though large truck traffic accounts for only 7.7 percent of the total vehicle-kilometers traveled on Houston freeways). Furthermore, lost or spilled loads and truck overturns account for nearly one-half of the major incidents in Houston. Information on incident severity and duration is also presented.

Examination of factors affecting freeway incident clearance times: a comparison of the generalized F model and several alternative nested models

“…Incidents involving a single vehicle cleared 39.3% sooner than multi‐vehicle incidents. While this finding differs from the results of a study in Houston, TX that analyzed major freeway incidents, the latter study focused on incidents that blocked a lane for 45 minutes to an hour. The clearance times in this study were generally much shorter (average 9.81 minutes), so as additional vehicles are affected, clearance times would be expected to increase accordingly.…”

How automated speed enforcement may reduce travel time variability and result in travel time savings: The case study of the loop 101 speed enforcement program in Scottsdale, Arizona

“…Since it is not possible to simulate all possible crash scenarios, the two aforementioned types of NR congestion conditions (i.e., 1-lane blockage and 2-lane blockage) were applied. For each condition, the median incident duration (68 min) described in the data description section was used as the blocking duration, since the distribution of incident duration is highly skewed to the right as shown in previous studies (Skabardonis et al, 1996;Ullman and Ogden, 1996). In addition, each condition was simulated at the 6 enforcement camera sites (3 sites per direction) to reflect the level of influence across sites within the enforcement zone.…”

“…To avoid overestimation of the change in the daily TTV, the NR states (the lane blockage states caused by crashes) were assumed to be related only to the injury crashes, since the PDO crashes generally have relatively minor impacts on traffic (Ullman and Ogden, 1996). Thus, the estimates of π and λ for total injury crashes in Table 1 were only used to estimate the probabilities of the NR state.…”