• Increase font size
  • Default font size
  • Decrease font size
Home People Viewscape

Travel Route Ratings for Roadway Travel Units

Status and Trend

Interpretation and Commentary


Click to interpret this icon

Status: At or Somewhat Better than Target
Trend: Moderate Improvement
Confidence: High


  • Relevance - This indicator tracks long-term, cumulative changes in scenic conditions along major roadways in the Region. It accounts for the urban, transitional, and natural landscapes that the roads pass through. Tracking these changes is important because it provides a measure of how changes in land use and development over time affect scenic conditions. Today, scenic conditions along Lake Tahoe’s major roadways are, on average, better than they were in 1982. The trend has been an improvement in conditions since 1991.
  • Adopted Standards  - To secure threshold attainment, the composite score of those roadway travel routes with a 1982 score of 15.5 or greater must be maintained at the level they were in 1982, and the composite score of all roadway travel routes with a 1982 score of 15 or less, must improve until the minimum score of 15.5 is reached.
  • Indicator - Roadway Travel Unit Composite score, which is a unit-less, numerical rating consisting of the sum of the ratings given to six different aspects of the landscape within each travel unit.
  • Status – As of 2011, 33 of the 54 (61 percent) Roadway Travel Units were determined to meet the Threshold Standard, while 21 (39 percent) did not. Of the 54 units, it was determined that zero percent are “considerably better than target,” 61 percent are “at or somewhat better than target,” 37 percent are “somewhat worse than target,” and two percent were “considerably worse than target.” When scenic evaluation units were aggregated according to the methods outlined in the methodology section of this report, the overall average status score of roadway travel units was = 0 and consequently determined to be “somewhat better than target.”
  • Trend –  In 1982, when Scenic Threshold Standards were first adopted, there were 23 Roadway Travel Units out of a total of 46 (50 percent) that did not meet the minimum standard. Of the 54 current units, it was determined that zero percent were in “rapid improvement,” 28 percent were in “moderate improvement,” 72 percent were in “little or no change,” zero percent were in “moderate decline,” and zero percent were in “rapid decline.”   When scenic evaluation units were aggregated according the methods outlined in the methodology section of this report, the overall average aggregation score for trend of roadway travel units was = 1 and consequently determined as “moderate improvement.” Since 1982, scenic conditions in nine of the original non-attainment units have improved such that the composite score now equals or exceeds the Threshold Standard.

Click here for more information...

  • Confidence  - 
    • Status - A documented, reviewed, and accepted monitoring protocol was used to guide the collection, analysis, and reporting of the scenic monitoring data. It was collected according to procedures outlined in the 1982 Study Report for the Establishment of Environmental Threshold Carrying Capacities (TRPA 1982b), and the Status and Trend Monitoring Report (DRAFT) for Scenic Resources in the Lake Tahoe Basin (TRPA 2010), which set forth a methodology for measuring change in scenic quality over time. The methods are consistent with those employed by the U.S. Forest Service, and are considered standard practice. This equates to a “high” confidence determination for status.
    • Trends - Basin-wide monitoring of travel route ratings occurred in 1971, 1982, 1986, and as part of the 1991, 1996, 2001, 2006, and 2011 Threshold Evaluations. This represents the most extensive and well-documented chronology of change to resources available within TRPA’s entire threshold-related monitoring record outside of Lake Tahoe monitoring efforts. Consequently, overall confidence in trend determination is “high.”
    • Overall Confidence - Because there is high confidence in the determination of both status and trend, a “high” determination is assigned to the overall status and trend determination.
  • Human and Environmental Drivers - The primary drivers affecting scenic quality in the Lake Tahoe basin are land use, land and resource management activities, and the visual/aesthetic characteristics of manmade development.
  • Monitoring Approach – Field surveys are conducted every five years by a team of qualified professionals (using established protocols), to examine and evaluate scenic conditions along major roadways in the Basin, the shoreline of Lake Tahoe, and at public recreation sites and bike trails. Ratings from prior evaluations are reviewed. Updated ratings are assigned as warranted, based on current conditions.
  • Monitoring Partners – U.S. Forest Service and Tahoe Regional Planning Agency.


  • Monitoring Plan
  • Conceptual Model


Map showing the distribution of roadway travel unit Threshold Standard status in the Lake Tahoe Region, 2011. (Source data: TRPA Scenic Threshold Monitoring Data).

Trend Charts

Chart data not available at this time.

Additional Info



Additional Information

  3. Conceptual Model:
  4. Monitoring Plan:
Last Updated on Friday, 31 August 2012 08:41