Implementation and Evaluation of the Sacramento Regional Transportation Management Center Weather Alert Notification System
This project, part of a FHWA-sponsored study of Traffic Management Center (TMC) weather integration strategies, aims to integrate road-weather information into the Caltrans District 3 Regional Traffic Management Center (RTMC) operational advisory functions by implementing an automated weather alert notification system. This system is expected to provide timely traveler and road weather information to the public, particularly regarding fog, wind, and frost conditions that can severely affect travel safety and mobility. The report evaluates the results and benefits achieved to date.
The evaluation examined four adverse weather events that occurred in the Sacramento region between December 2009 and April 2010 - one fog event, and three wind events. Post-implementation data were obtained from the Road Weather Information System (RWIS) sensors, the alert system records, and message sign records. In addition, pre- and post-implementation interviews were conducted with selected operators.
Quantitative findings were examined for three main measures of performance: 1) timeliness of issuance of warnings and alerts, 2) timeliness of operator activation and deactivation of messages, and 3) adequacy of use of available message signs in the valley relative to those sensor sites that were reporting adverse weather conditions.
Overall, the operators valued the warnings and alerts provided by the weather notification system, though they felt it necessary to verify their accuracy before taking any actions based on them. They perceived that sensor data quality has improved over the period of implementation. Operators stated that the automated alert system has made them more aware and allowed them to be more responsive to events as they unfold. However, the level of performance must improve before the benefits to the traveling public of enhanced mobility and safety during periods of inclement weather and dangerous road conditions can be realized.
Quantitative findings are described below:
- Timeliness of Alerts. Across the four event periods analyzed, alerts were used in a timely and accurate way. In 16 out of 18 times (88.9 percent) alerts were issued 'on time,' defined as within +/- 10 minutes of the time when the weather condition broke its defined threshold value at the beginning of the event. In the other two cases, one alert was issued a half hour after the start of the event and in the other case, no alert was issued.
- Timeliness of Message Activation. Fifteen individual sensor-reported weather events that exceeded threshold and/or lasted longer than 16 minutes should properly have had weather warning messages posted; 13 of them did, and two had no messages posted. For those events with some message coverage, coverage ranged from 27 to 100 percent of the duration of the event. Out of the 13 events with message coverage, 11 had coverage over 75 percent of the duration of the event.
- Adequacy of Message Coverage. The number of CMS, EMS and LED signs used was significantly less than the number of signs recommended in the RTMC policy guidelines. For the fog event, only 2 out of 8 opportunities to activate primary signs were used. For the three wind events, 12 out of 43 (28 percent) opportunities were used. The ratio of messaging improved over time, with 7 out of 17 (41 percent) used in the April event.
- Timeliness of Message Deactivation. For 14 sensor-reported events for which messages were activated, the period from the end of the event to message deactivation ranged from 18 minutes to 8 hours and 44 minutes, with an average lag time of 4 hours and 14 minutes. The experience shows that there were a number of periods during which messages were left active much longer than needed or desired.