Assessing Winter Storm-Related Non-Recurring Congestion in the Salt Lake Valley. Ralph Patterson 1 , Randy Graham 2 , Kevin Barjenbruch 2 , Glen Merrill 2 , Glenn Blackwelder 1 , Brett Hansen 3 , Mike Holts 3 , Julie Miller 1 , Mike Seaman 2 , Jeff Williams 3 , Audra Yocom 1 , Carol Werner 4 - PowerPoint PPT Presentation
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Assessing Winter Storm-Related Assessing Winter Storm-Related Non-Recurring Congestion in the Non-Recurring Congestion in the Salt Lake Valley Salt Lake Valley Ralph Patterson Ralph Patterson 1 , , Randy Graham Randy Graham 2 , Kevin Barjenbruch , Kevin Barjenbruch 2 , Glen , Glen Merrill Merrill 2 , , Glenn Blackwelder Glenn Blackwelder 1 , Brett Hansen , Brett Hansen 3 , Mike Holts , Mike Holts 3 , , Julie Miller Julie Miller 1 , Mike Seaman , Mike Seaman 2 , Jeff Williams , Jeff Williams 3 , Audra Yocom , Audra Yocom 1 , , Carol Werner Carol Werner 4 1 Utah Dept of Transportation, Traffic Operation Center, Utah Dept of Transportation, Traffic Operation Center, Salt Lake City Salt Lake City 2 National Weather Service, Salt Lake City National Weather Service, Salt Lake City 3 NorthWest Weathernet, Salt Lake City NorthWest Weathernet, Salt Lake City 4 University of Utah, Salt Lake City University of Utah, Salt Lake City AMS WAF/NWP Meeting – Omaha, NE
Transcript
Assessing Winter Storm-Related Assessing Winter Storm-Related Non-Recurring Congestion in the Non-Recurring Congestion in the
Salt Lake ValleySalt Lake Valley
Ralph PattersonRalph Patterson11, , Randy GrahamRandy Graham22, Kevin Barjenbruch, Kevin Barjenbruch22, Glen Merrill, Glen Merrill22,,
Glenn BlackwelderGlenn Blackwelder11, Brett Hansen, Brett Hansen33, Mike Holts, Mike Holts33, Julie Miller, Julie Miller11, Mike , Mike SeamanSeaman22, Jeff Williams, Jeff Williams33, Audra Yocom, Audra Yocom11, Carol Werner, Carol Werner44
11Utah Dept of Transportation, Traffic Operation Center, Salt Lake Utah Dept of Transportation, Traffic Operation Center, Salt Lake CityCity
22National Weather Service, Salt Lake CityNational Weather Service, Salt Lake City33NorthWest Weathernet, Salt Lake CityNorthWest Weathernet, Salt Lake City
44University of Utah, Salt Lake CityUniversity of Utah, Salt Lake City AMS WAF/NWP Meeting – Omaha, NE
OutlineOutline PartnersPartners
Weather Impacts on Weather Impacts on Roads in the Salt Lake Roads in the Salt Lake City metro City metro
Comparison of travel Comparison of travel impacts associated with impacts associated with two winter weather eventstwo winter weather events
Future workFuture work
AMS WAF/NWP Meeting – Omaha, NE
Photo courtesy UDOT
Unique CollaborationUnique Collaboration Federal (NWS), state (UDOT), Federal (NWS), state (UDOT),
and private meteorologists and private meteorologists (Northwest WeatherNet), (Northwest WeatherNet), academia (University of Utah)academia (University of Utah)
Meteorologists embedded at Meteorologists embedded at the UDOT Traffic Operations the UDOT Traffic Operations Center (TOC)Center (TOC) Meteorologists with UDOT and Meteorologists with UDOT and
Northwest WeatherNetNorthwest WeatherNet
Direct involvement of UDOT Direct involvement of UDOT Traffic EngineerTraffic Engineer
AMS WAF/NWP Meeting – Omaha, NE
Increased Demands…Increased Increased Demands…Increased Commute TimesCommute Times
Rapid population growthRapid population growth 23.5% increase between 2000 and 200823.5% increase between 2000 and 2008
Increased demand on existing Increased demand on existing infrastructureinfrastructure
Congestion results in annual cost of Congestion results in annual cost of $250 million in Utah (UDOT)$250 million in Utah (UDOT) Recurring (i.e., AM/PM peak commute Recurring (i.e., AM/PM peak commute
Inclement weather plays a significant Inclement weather plays a significant role in non-recurring congestionrole in non-recurring congestion Delays, mobility, productivity, and safetyDelays, mobility, productivity, and safety ““Large weather events cause trips to Large weather events cause trips to
take 40-50% longer” (UDOT report)take 40-50% longer” (UDOT report)
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Photo courtesy UDOT
So…So…
Which event will produce the Which event will produce the biggest impact? biggest impact?
A. 1-3” between 200 PM - A. 1-3” between 200 PM - 600 PM 600 PM
B. 4-6” between 1000 PM - B. 4-6” between 1000 PM - 400 AM400 AM
C. 6-8” between Noon - C. 6-8” between Noon - 1000 PM1000 PM
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Factors in Event ImpactFactors in Event Impact Time of dayTime of day Day of weekDay of week Snowfall ratesSnowfall rates Snowfall amountsSnowfall amounts Road temperaturesRoad temperatures Mitigation strategiesMitigation strategies HolidaysHolidays Public perception/preparednessPublic perception/preparedness
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Weather Impact on Weather Impact on CommuteCommute
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Travel Time Index (TTI) – Measure of the increase in Travel Time Index (TTI) – Measure of the increase in travel time associated with congestion, incidents and travel time associated with congestion, incidents and
weather.weather.
Example commute of 20 minutesExample commute of 20 minutesTTI of 1 = 20 minutesTTI of 1 = 20 minutes
TTI of 1.3 = 20 x 1.3 = 26 minutesTTI of 1.3 = 20 x 1.3 = 26 minutesHigh TTI (congestion and delays) dominated by weatherHigh TTI (congestion and delays) dominated by weather
““This is a striking finding – but it seemed intuitive on further This is a striking finding – but it seemed intuitive on further consideration. The only things that affect the entire road consideration. The only things that affect the entire road system around Salt Lake City are snowstorms, or major system around Salt Lake City are snowstorms, or major holidays. Other sources of delay (crashes, thunderstorms, holidays. Other sources of delay (crashes, thunderstorms, congestion) tend to be more localized.” (UDOT)congestion) tend to be more localized.” (UDOT)
Image courtesy Glenn Blackwelder
Data…Data…Data…Data…Data…Data… ~20 events from the winter ~20 events from the winter
2008-09’2008-09’
Collection of weather and traffic Collection of weather and traffic datadata Radar and satellite dataRadar and satellite data Mesonet observationsMesonet observations Road temperaturesRoad temperatures Traffic informationTraffic information Plow driver reportsPlow driver reports Accident informationAccident information
Investigation of NWS and UDOT Investigation of NWS and UDOT statementsstatements Discussion of societal impactsDiscussion of societal impacts Does lead time impact volume?Does lead time impact volume?
5 Jan 2009 – 5 Jan 2009 – Well forecast….butWell forecast….but
1-3” forecast for Salt Lake 1-3” forecast for Salt Lake Valley prior to onset Valley prior to onset Verified wellVerified well
Winter Weather Advisory Winter Weather Advisory issued near onset issued near onset Based on potential impacts on Based on potential impacts on
the afternoon commutethe afternoon commute
Minimal discussion of impact Minimal discussion of impact in days leading up to eventin days leading up to event Several significant storms had Several significant storms had
preceded this eventpreceded this event
Photo courtesy KSL-TV
Road Considerations and Road Considerations and ImpactsImpacts
Road temperatures in the Road temperatures in the low to mid 20s Flow to mid 20s F Snow stuck to roads at onsetSnow stuck to roads at onset
??Limited mitigation prior ??Limited mitigation prior to event??to event??
Over 180 accidents in Salt Over 180 accidents in Salt Lake and Utah Counties Lake and Utah Counties alonealone
Worst commute of the Worst commute of the seasonseason
5 Jan 2009 - Road temperatures ~ 420 PM
MST
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19 December 200919 December 2009 More ‘ramp-up’ to the eventMore ‘ramp-up’ to the event
Area Forecast Discussion – 442 PM 17 Dec Area Forecast Discussion – 442 PM 17 Dec 2008 - 2008 - ……With very cold temps expect snow to With very cold temps expect snow to rapidly accumulate on area roadways…rapidly accumulate on area roadways…
Winter Storm Warning – 302 PM 18 Dec Winter Storm Warning – 302 PM 18 Dec 20082008……Snow expected to rapidly accumulate Snow expected to rapidly accumulate along area roadways and result in along area roadways and result in treacherous driving conditions…treacherous driving conditions…
..Much of this snow may be occurring ..Much of this snow may be occurring during the late afternoon and early hours during the late afternoon and early hours which would have a very significant impact which would have a very significant impact on the evening commute…on the evening commute…
Add image
Roads temperatures Roads temperatures remained near 30 degrees remained near 30 degrees through the event through the event More effective mitigationMore effective mitigation
Level of service remained Level of service remained higher throughout the higher throughout the eventevent
Aggressive mitigation Aggressive mitigation prior to and during eventprior to and during event
3-7” storm total 3-7” storm total 19 Dec 2008 - Road temperatures ~ 400 PM
MST
Road Considerations and Road Considerations and ImpactsImpacts
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Speed and Speed and FlowFlow
January 5January 5thth Event Event Speed trough on the 5Speed trough on the 5thth was was
lower lower Bigger eventBigger event Reduced flow due to Reduced flow due to
congestion…reduced capacity congestion…reduced capacity of system due to slow travel?of system due to slow travel?
December 19December 19thth Event Event Increase in flow (above Increase in flow (above
normal) prior to snowfall normal) prior to snowfall onsetonset
Well forecast onset?Well forecast onset? Dip right at peak traditional Dip right at peak traditional
max flow time due to increase max flow time due to increase in snowfall intensityin snowfall intensity
A lot of similarities between A lot of similarities between the two events…the two events…
Drop in discretionary Drop in discretionary traveltravel
Travel is not displaced in Travel is not displaced in time (i.e., flow doesn’t time (i.e., flow doesn’t recover)recover)
Speeds and flow drop off Speeds and flow drop off rapidly right after onsetrapidly right after onset
I-15 SB 8600s Snow Event (1/5/09)
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Time of Day
Mean Flow
Event Flow
Event Speed * 100
I-15 SB 8600s Snow Event (12/19/08)
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
Flow
Mean Flow
Event Flow
Event Speed * 100
Level of Service (LOS)Level of Service (LOS) Freeway level of service is defined by the density of vehicles on the Freeway level of service is defined by the density of vehicles on the
road (vehicles per mile per lane), and is a measure of a driver's road (vehicles per mile per lane), and is a measure of a driver's freedom to maneuverfreedom to maneuver
LOS A - Free flow - the ability to maneuver is unimpededLOS A - Free flow - the ability to maneuver is unimpeded
LOS B - Reasonably free flow - slight restriction in maneuverability LOS B - Reasonably free flow - slight restriction in maneuverability
LOS C - Ability to pass or change lanes is not always assured, but LOS C - Ability to pass or change lanes is not always assured, but posted speed is maintained, more driver vigilance requiredposted speed is maintained, more driver vigilance required
LOS D - Slight reduction in speeds, ability to pass or change lanes LOS D - Slight reduction in speeds, ability to pass or change lanes reduced, traffic stream has little space to avoid disruption, driver reduced, traffic stream has little space to avoid disruption, driver comfort reducedcomfort reduced
LOS E - Ability to pass or change lanes is constrained, flow is LOS E - Ability to pass or change lanes is constrained, flow is unstable, speed varies, road is at capacity, drivers are uncomfortableunstable, speed varies, road is at capacity, drivers are uncomfortable
LOS F - A breakdown in vehicular flow - each vehicle follows another LOS F - A breakdown in vehicular flow - each vehicle follows another at minimum safe spacing due to demand exceeding capacity.at minimum safe spacing due to demand exceeding capacity.
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So, how was the So, how was the commute?commute?
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January 5January 5thth event: event:
Note the significant Note the significant difference between Mon difference between Mon and Tueand Tue
As flow goes down there As flow goes down there is high density of vehicles is high density of vehicles on the roadwayon the roadway
No space, very difficult No space, very difficult to switch lanes, vehicles to switch lanes, vehicles move in lock step, frequent move in lock step, frequent stopsstops
December 19December 19thth event: event:
Higher level of service Higher level of service indicates that people are indicates that people are moving (albeit at a reduced moving (albeit at a reduced speed, in this case)speed, in this case)
Not completely packed on Not completely packed on the roads there is spacingthe roads there is spacing
Difference between Thu Difference between Thu and Fri is not that and Fri is not that significant significant
Friday afternoon is Friday afternoon is typically a heavier commute typically a heavier commute than Monday afternoonthan Monday afternoon Flow and speed showed Flow and speed showed similar trends, but driver similar trends, but driver perception of 19 December perception of 19 December commute likely very commute likely very different than 5 January different than 5 January commutecommute Better prepared? More Better prepared? More effective mitigation? effective mitigation?
Uncertainty and ImpactUncertainty and Impact
Public Response
Meteorology Road Conditions
Impact
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It is important to note that one of the most cost effective solutions for mitigation of the
congestion problem is driver habit modification. – UDOT
“This is also an encouraging finding because it suggests that the highest overall delay may be predictable (but perhaps not avoidable) with accurate weather forecasts.” – UDOT
2007 Congestion Report
Future WorkFuture Work Human BehaviorHuman Behavior
With confidence in forecast and road With confidence in forecast and road impact, can we influence response?impact, can we influence response?
Effective communication strategies?Effective communication strategies? Increased penalty for false alarms?Increased penalty for false alarms?
Project with NWS/UDOT/NWN and Project with NWS/UDOT/NWN and University of Utah - Winter of 09-University of Utah - Winter of 09-10’ 10’ Two to three events Two to three events ~400 professionally administered ~400 professionally administered
driver surveysdriver surveys Levels of awareness Levels of awareness Sources of informationSources of information Responses to road/weather info Responses to road/weather info
(behavior modification)(behavior modification) Detailed correlation of weather to Detailed correlation of weather to
