Denali Park Road Capacity Study

 

NPS Photo / Kent Miller

 

The road study was completed in 2012 with the approval of the Denali Park Road 2012 Vehicle Management Plan. This plan marks the start of a new era in the management of the park road.

 

The colored dots on the map of Denali (between Teklanika and Toklat rivers) show the hourly location of 18 GPS-collared sheep during the summer of 2007. Individual sheep are represented by dot color. The park road is shown in red. Dall sheep crossed the park road at Miles 33-38, 44-48, and 51-53.

Study History

In 2006, Denali began a multidisciplinary study designed to optimize visitor experience along the park road while protecting wildlife. Since 1972, traffic on the park road has been limited mostly to buses, and since 1986, a use limit of 10,512 vehicle trips annually has been in effect. Faced with increasing visitation and pressure to defend or change the limits to road traffic, park managers have designed a study to develop a greater understanding of the impacts of traffic volume and traffic patterns on the physical, biological, and social environment of the park. The study was comprised of three primary components and took place from 2006 to 2012.

Wildlife Movements

The heat map below demonstrates the three bears (#s 573, 576 and 586) tracked in summer 2006. The fainter, bluer colors indicate areas infrequently visited by the bears, while the yellow and red (warmer) areas indicate areas where those bears spent more time.

 

 

To examine potential impacts of Park Road traffic on wildlife movements and distribution, researchers deployed GPS collars on 20 Dall's sheep and 20 grizzly bears within the road corridor. Location information and movement paths of collared animals were modeled with habitat and traffic data to determine possible relationships between vehicles on the Park Road and wildlife behavior.

Viewable in Google Earth, data showing the movements of three of the collared bears from the summer of 2006 can be found below. Also available are the movements of two groups of Dall sheep in the summer of 2007. Download the files and open them in Google Earth.

• Bear 573 (1759kb)
• Bear 576 (1727kb)
• Bear 586 (1686kb)
• Sheep 607 (1652kb)
• Sheep 610 (1756kb)

Displaying thousands of points, the data demonstrate what parts of the park these animals frequent, and when.

Visitor Survey

Researchers examined the expectations and quality of experiences of Denali Park Road vehicle users. As part of this study, visitors were asked to identify and describe issues important to their experience on the Denali Park Road. The results of these interviews were used to determine indicators and help set standards for visitor experience on the Park road. Park managers are using the indicators and standards to evaluate and manage vehicle.

• 2007 Quantitative Visitor Experience Survey
• 2009 Visitor Experience Report

 

Traffic Model

Traffic patterns on the Denali Park road are unique and affected by predictable and unpredictable factors such as locations and type of wildlife sightings, numbers and type of buses on the road each day, weather, and road maintenance. Researchers used GPS and wildlife sighting data collected from vehicles driving the park road in 2006/2007 to create a traffic model to simulate the location and timing of vehicles on the park road.

Over the past several years, park ecologists have been using new techniques and technology, coupled with GPS data from 2012-2016, to develop a hybrid agent/behavior-based, empirical traffic model more capable of simulating specific vehicle behaviors. Our model describes several variables including vehicle types, probabilities of animal presence by animal type, stopping probabilities and durations specific to animal type, stopping location probabilities and travel speed over 28 road segments creating over seven billion combinations in the current model version. The model enables managers to test proposed or theoretical bus schedule scenarios and wildlife sightings quantify their effects on the seven main VMP indicators. The results will be used to proactively evaluate changes to the bus schedule to ensure those changes will not have a detrimental impact on parking resources or visitor experience.

Study Goals

Ultimately, a comprehensive model of park road traffic was developed to predict the effects of changes in traffic volume and timing on visitor experience and wildlife movements. The model results informed the selection of a preferred alternative presented in the Vehicle Management Plan Environmental Impact Statement (EIS). This model suggested that an increase in traffic volume was feasible. The next step is an experimental increase in road traffic, timed so as to produce the greatest value in understanding impacts, as part of a Before-After Condition-Change Assessment (BACCA) study. The goal of the road study was to provide park managers with a tool to make well-informed, science-based decisions about the future of traffic on the park road.

Developing Indicators and Standards

Results from the road capacity study were used to select seven indicators of desired resource and visitor experience conditions.

Three of the indicators restrict the amount and timing of vehicle traffic to protect wildlife:

• Hourly 10-minute gaps in traffic at five sheep crossings,
• An hourly limit to night-time (10 p.m. to 6 a.m.) traffic, and
• An hourly limit to large (>80,000 gross lbs) vehicles

Three indicators set limits on vehicle crowding based on results of the visitor surveys:

• The number of vehicles at a stop to view wildlife,
• The number of vehicles parked at rest stops, and
• The number of vehicles visible in four iconic viewscapes.

The final indicator reflects the effectiveness of the transportation system:

• Amount of time a hiker waits to catch an eastbound bus.

Results were also used to set quantitative standards for each indicator to ensure that desired conditions are maintained. Meeting the standards means success in managing the park road for its natural ecology and visitor experience.

Download the Table of Indicators and Standards

Additional Information

• The Vehicle Management Plan EIS
• Road Ecology Program: Protecting Resources and Values Along the Park Road
• 2006 Grizzly Bear Report - Habitat Use and Movement Relative to the Park Road
• 2006 - 2009 Road Study Summary
• Annual Reports, Background, & Operating Procedures