For an overview of how Curvature can fit into your trip planning, see How to Use. This page will detail the mechanics of viewing the files.
The Curvature program generates map files that can be viewed in Google Earth. These map files are generated for all regions of the world and are refreshed every two weeks to take into account updates to the underlying data sourced from the Open Street Map.
Step 1: Install Google Earth
To view Curvature files, you will first need to install Google Earth on your computer. Google Earth is a free program available for both desktop computers as well as mobile devices.
Step 2: Download a Curvature KML file
Head to http://kml.roadcurvature.com/ to download a compressed KML file for your region. Most people will want to download the “c_1000” version of the files as these highlight only the most twisty roads — those with approximately 1km or more of curves.
The KML files are ordered by continent, country, and state/province.
Click on the “c_1000” link to download the file to your computer, usually it will end up in a “Downloads” folder on your computer.
Step 3: Open the KML file in Google Earth
Find the KML file in your downloads folder, it will be named something like “vermont.c_1000.kmz”.
Double-click on it to open it in Google Earth. If for some reason it doesn’t open, first open Google Earth and choose “File » Open…” and select the file.
4. Look for curvy roads
After you’ve opened the file in Google Earth you can zoom around and identify curvy roads:
Clicking on a road will pop up details indicating any surface tags for each segment as well as length and ‘curvature’:
Step 5: Plan your route
Google Earth doesn’t have great built-in route-planning tools, so it is usually easiest to simply identify the curvy roads via the Curvature files in Google Earth, then plan your route using other route-planning software such as Garmin Base Camp, Google Maps, or similar.