Road Condition and Treatment Module Overview, Upgrades, Examples and Limitations

1. Road Condition and Treatment ModuleOverview, Upgrades, Examples and Limitations Robert Hallowell MIT Lincoln Laboratory bobh@ll.mit.edu Presented by: Bill Mahoney, NCAR

2. Outline • Background • Modifications for Release 4.0 • Example cases • Limitations • Summary

3. Road Condition & Treatment Module The RCTM can be driven by any weather time series data set! Weather Prediction Engine Road Condition & Treatment Module • Time Series Weather Data • Air Temperature • Dew Point • Wind Speed • Wind Direction • Insolation (direct and indirect) • Precipitation Type • Precipitation Rate (liquid) • Generates: • Pavement Temperatures • Treatment Recommendations • Road Condition Data • Treatment Reasoning Text

4. Road Condition-Treatment Components Storm Characterization Treatment Plan Chemical Application Weather Variables Road Weather Conditions - Pavement temp - Snow depth Rules of Practice Plowing RWFS Chemical Concentration Display / User Interface

5. Storm Life Cycle Characterization Post-storm In-storm Pre-storm Multi-phase precipitation (eg. Rain to snow) Multiple road temp trends (eg. Warm to in-range) Timing: stop, start, duration Precip: total frozen/liquid Road Temp trends Blowing snow Road Temp trends CAPTURE Impending storms may require pre-treatments Roads may refreeze IMPACTS Dry Road Start of Precipitation End of Precipitation 6-12 Hour Lead Time Multiple treatments may be needed Varied precipitation types or road temperatures may change treatment strategy Pre- and Post-storm conditions may impact treatment strategy

6. Rules for Treatment Recommendations • Perform Pre-treatment operation if: • Precipitation type starts as freezing rain • Precipitation type starts as snow and road temperatures are in-range • Suppress Pre-treatment if: • Storm type starts as rain • Roads are cold AND blowing snow is present • Pre-storm roads or initial In-storm roads are warm • Perform Plow-only Operations if: • In-storm road temperatures are Too Cold or In-range moving toward Too Cold • In-storm road temperatures are In-range or Too Cold to In-range AND a Blowing Snow threshold is met • Roads are warm In-storm and Post-storm • All other In-storm road conditions AND Post-storm road temperatures are Too Cold Plow treatments clear snow in first hour and then allow snow to accumulate

7. Rules for Treatment Recommendations • In-storm recommendations: • Chemical treatments offset to start before trigger point (route time) • Blowing snow during a storm combined with below 20 oF roads will suppress chemicals and recommend plow only treatments • Cold (<14 oF) post-storm road temps will change treatment plan from chemicals to plow-only to avoid post-storm refreeze • Chemical treatments may be increased to cover short duration storms using one application • Post-storm recommendations: • Dry road time • Protect road from re-freezing

8. Calculating Chemical Treatments Effective Chemical Range Chemical Effectiveness Dilution Factors 35 30 25 20 15 Precipitation Sodium Chloride Temperature (Deg F) Solution and Ice 10 Solution and Salt Splatter 5 Magnesium Chloride Traffic 0 Calcium Chloride Liquid runoff & Evaporation -5 Ice and Salt -10 0 5 10 20 25 30 15 Weight Percentage of Salt

9. Sample Treatment Recommendation / Selection

10. Updates for Release 4.0 - RCTM • Basic configuration of chemicals adjustable per route (instead of for the entire system) • Rates and chemical types • The form of the chemical (dry, pre-wet, liquid) – changes splatter and loss rates • Independent control of pre-treatment type (salt, MgCl2, etc.) • Added several new chemicals: Caliber, Ice Slicer, CMag Acetate, K Acetate • Added handling of multiple chemical types for user-entered treatments • For example: Start with pre-wet salt and follow-up with liquid mag-chloride (system assumes that residual salt at time of mag-chloride is treated like mag-chloride – little data exists for “stacking” of chemical types. The recommended treatments do not have the capability to produce multi-chemical recommendations

11. Updates for Release 4.0 - RCTM • Controlling treatment strategy: • Users can now pre-configure two types of treatment strategy: “ONTRIGGER” and “CONTINUOUS”. • Ontrigger mimics the traditional strategy of treating and then re-treating only when the first treatment becomes too weak. • Continuous is utilized for aggressive maintenance and it attempts to have trucks on the road continuously. Continuous treatments are more frequent but with lower application rates that Ontrigger events. • Treatment triggers modified: • Delay treatment when rain is occurring prior to the trigger event (e.g., snow, ice). • Added additional sensitivity parameters to make fine-tuning treatment rates simpler. • The form of the chemical (dry, pre-wet, liquid) – changes splatter and loss rates. Independent control of pre-treatment type • Snow on the road at startup is now handled as a trigger for treatments.

12. Updates for Release 4.0 - RCTM • Miscellaneous changes • The blowing snow potential algorithm is now integrated into RCTM to: • (1) Increase application rates during hours of blowing snow • (2) Inhibit chemical applications when there is light snow and very cold roads • Track the phase of the water on the road (wet, chem-wet, chem-ice, snow and ice) • Added treatment explanation strings

13. Sample Cases Colorado 2004-05 • Available test cases • 12 days total • 11 treatment days • Only 2 storms over 5 inches • However, light snow events were critical • Data capture • Snow rates not adequate • Pavement temperature • Convoluted “truth” • Road condition – Snow depth comparison

14. November 10-11, 2004 Colorado Road temp drops below freezing Treatments triggered to protect road from freezing Protecting roads after precipitation Road still wet (icon not shown)

15. November 10-11, 2004 Colorado Road temp drops below freezing, but in-range Snow Event 1.5 inches Multiple treatments triggered to handle snow

16. November 27-28, 2004 Colorado Road temp below freezing, but in-range Snow Event 2.5 inches Pre-treatment + multiple “CONTINUOS” solid treatments

17. April 9, 2005 Colorado Road temp drops below freezing, but in-range Snow Event 9.5 inches Multiple “ONTRIGGER” solid treatments

18. Treatment Recommendations Lessons Learned • Road temperature calculation for treatment recommendations • Assume clear roads or calculate based on actual conditions? • Using forecasted weather requires auto-restarts of SNTHERM each time snow is cleared. This causes instabilities in the road temperatures due to initialization • Using “cleared” road conditions provides consistent road temperatures, but does not necessarily reflect actual conditions • Solution: More research. Better handling of SNTHERM restart or incorporating “slush” layer into SNTHERM. • Rules verification • “Perfect” weather ingest tedious • Solution: Build playback system to allow easy ingest • Mixed operations • Overwhelming snows / blowing snow (upgraded in release 4.0 to text warning that current treatment is insufficient) • Solution: Allow multiple level treatments

19. Treatment Recommendations Lessons Learned (con’d) • Rules for recommending multiple chemical types in a single storm • Many jurisdictions use this technique when road temperatures drop drastically in a storm. • Solution: Adjusting the algorithm to “lookup” the appropriate chemical would be straight-forward. Keeping track of the effectiveness of individual chemicals would be harder. • Weak snow events • Difficult to forecast • Solution: Tactical use of radar estimated precip. & tracking • Actual road conditions are inconsistent with recommended treatment logic • The system can only estimate the effect of recommended treatments • Solution: Need better feedback of actual treatments and road conditions