Compound Friction Score
The Compound Friction Score (CFS) is a second way to rank routes, alongside collisions per mile, based on how demanding a route's turns are rather than just its crash history.
The idea
A hard left immediately after a right turn asks a lot more of a driver than the same two turns spread apart, even on streets with identical crash histories, and CFS puts a number on that.
Example: Route A turns right and three seconds later crosses two lanes to turn left, while Route B makes the same two turns a quarter mile apart with a light in between, so CFS scores Route A higher even if their crash histories match.
How it's calculated
Every route comes back as a list of steps, and each step's maneuver (turn, merge, ramp, roundabout, or nothing for a plain "keep going") adds a weight to the route's total:
| Maneuver | Weight |
|---|---|
| Straight / keep going | 0 |
| Slight turn (left or right) | 1 |
| Ferry | 1 |
| Right turn | 2 |
| Fork (left or right) | 2 |
| Freeway ramp (on or off) | 3 |
| Sharp right turn | 3 |
| Left turn | 3 |
| Roundabout | 3 |
| Sharp left turn | 4 |
| U-turn | 4 |
| Merge | 5 |
Left turns and U-turns weigh more than right turns because they cross oncoming traffic, and merging onto a freeway weighs the most since that's where fast cross traffic converges.
SafetyFirst also adds a compounding bonus when two significant maneuvers happen close together in time:
- Under 5 seconds apart: +6
- Under 10 seconds apart: +3
- Under 20 seconds apart: +1
That gap is measured in time, not distance, since the same 200 feet between two turns is nothing at a red light but a real scramble at 45 mph.
Limitations
CFS only looks at route geometry, so it doesn't know about actual traffic, weather, or intersection design, and it can't guarantee what happens on any one drive, so always drive safely and follow the law.
← Back to Home