8.1 PRSR 01-15-2020 - Laserfiche WebLink

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2 STATE of the TRAILS How We Calculate Our Ratings Our trail condition ratings are based on the premise that trails in excellent condition are smooth to ride and trails in poor condition are rough to ride. We measure how rough each trail is to ride using a metric called the “Trail Roughness Index”, or “TRI” for short. We created the TRI in 2016 as a method to objectively rate the condition of paved bike trails. We updated our methodology in 2018 to improve reliability and validity. Trail Roughness Index is measured by riding a trail with a device called an accelerometer mounted on the bike’s handle bars. When the bicyclist hits a crack or bump in the trail, the accelerometer measures the force of the jolt felt by the bicyclist. The TRI is a statistical summary of the accelerometer data that indicates the roughness of the ride. Low TRI scores indicate trails in excellent condition (TRI < 30) and high TRI scores indicate trails in very poor condition (TRI > 75). We used TRI scores to rate the condition of Minnesota’s paved state trail system on a segment-by-segment basis. Additionally, we assigned each trail an overall grade using a scale where “excellent” is equal to an “A” and “very poor” is equal to an “F”. The overall trail grade represents the condition of the trail’s average mile. All of our data was collected by a Parks & Trails Council intern. The intern rode nearly 600 miles of the paved state trail system on the Research Bike, an electric- assist bicycle equipped with cameras and sensors. All data was collected during the summer and fall of 2018. Our TRI scores are supplemented with photos taken during the data collection process. Photos were used to verify condition classifications and are helpful to visualize on-the-ground conditions. See Appendix A and Appendix C for more details on our methodology. How the Trail Roughness Index Works g-force on vertical (Z) axis: When a bicycle rides along a smooth trail, the accelerometer shows a relatively �lat line. As trails age, bumps and cracks start to form in the pavement. The accelerometer records these imperfections when the bicycle rides over them. When a trail is nearing the end of its useful life, bumps and cracks are prevalent. Accelerometer readings on such trails show a rocky, jagged line. Each “spike” on the accelerometer graph indicates a bump on the trail The Trail Roughness Index (TRI) measures the variation in g-forces felt by a bicyclist riding on a trail. The g-force is measured by an accelerometer in a bicycle-mounted iPhone and is recorded by an iPhone app.