City deploys new road weather technology
When a winter storm is forecasted to move in, city maintenance crews already have a maintenance plan in place. Many operation decisions may be made well before the storm has even started. In the past, those tasked with clearing roads have been forced to rely solely on road weather information obtained from pavement conditions outside of their jurisdiction. In many cases, the volume and types of traffic, pavement material and other environment factors on state roads could be much different than what is seen on local road networks. With salt brine and anti-icing practices, pavement temperature forecasts are critical to winter road maintenance success.
For many years most of the City's pavement temperature forecasts were developed utilizing road weather information from Iowa Department of Transportation (IDOT) interstate roadways using first generation road weather informations ystems (RWIS) stations. With the evolution of winter maintenance RWIS technologies and new leasing programs for the necessary equipment, there are now road weather information tools available to a broader base of end users. Now the critical data needed for local road networks is within reach.
Over the past few years, West Des Moines has deployed RWIS to monitor both road and bridge conditions in four locations. The systems are fixed-mount stations that have been installed along major arterial corridors on traffic signal mast arms. The systems have been installed strategically throughout the city to provide real time road conditions to supervisors and a contracted weather service provider.
The most recent system was installed on Westown Parkway over I-35/80. This dual-device system provides both road and bridge pavement conditions through one processer. The city has partnered with the IDOT to share information that is being gathered from the bridge mounted device. Since bridge deck temperatures vary greatly from road pavement temperatures, the data gathered by this equipment is critical in the operational decision process.
The RWIS stations are accessed via a personalized credentials from any web-enabled device. Furthermore, the systems report to a remote server via a cellular connection -- no hardwired communications connection needed. This is a tremendous advantage for a agency that does not have staff to monitor or maintain an in-house server and database. All the equipment is continuously monitored by the service provider to ensure the functionality of all components of the RWIS.
These systems provide information related to road surface conditions using infrared technology. This eliminates pavement deterioration concerns that pavement cutting or drilling could cause. Interference from maintenance operations is also minimized. The information collected includes surface temperature and surface conditions of the road such as: dry, wet, snow or ice covered. The thickness measurement of any water, ice or snow is given in millimeters and a friction coefficient is provided to determine slickness. Atmospheric conditions such as air temperature, relative humidity, and wind speed are also provided.
The weather information from all units is obtained from remote sensors with the exception of subsurface temperature. Subsurface temperature is obtained using a subsurface probe. These stationary systems also incorporate cameras to provide time lapse photographs to assist with evaluating surface conditions throughout the storm event.
This past winter, the city was asked to participate in a pilot project to test and evaluate snowpolow truck-mounted infrared RWIS devices. Along with West Des Moines, the pilot included the Colorado, Alaska and Idaho departments of transportation. Like the fixed mount RWIS units, these devices measured and provided data regarding various pavement and atmospheric conditions. Operators involved in this proejct provided feedback on the benefits they realized while using the units, along with areas where they felt improvements could be made. Two of the major equipment features the operators found extremely useful was the ability to get an actual road friction reading along with data on whether the road conditions were icy or wet. In many cases, operators determined that deicer applications were not necessary based on the information the devices were providing to them. Lower deicer use is both a financial and an environmental win.
The use of these systems for winter operations enabled West Des Moines Public Services staff to more effectively make informed decisions concerning the management of winter storm events. While the principle of using weather information to help guide granular and liquid application rates is not a new concept for city staff, they are now able to utilize real-time information obtained from their respective road network. Utilizing information gathered from the local road network takes much of the "guess work" out of data interpretation. Staff can now make material application recommendations with increased confidence since they have accurate surface and atmospheric conditions specific for their road network. Furthermore, the data produced by the RWIC is utilized by the CIty's contracted weather forecast service to provide site-specific forecasts and treatment recommendations. By utilizing the data provided and the proper use of deicing chemicals, the results have led to lower overall costs while maintaining expected levels of service goals.