Highlight positive impacts in impact mode

This issue is a bit of a placeholder, but I wanted to capture some values expressed in todays discussion

While discussing if we should pursue #127 (outcome: probably not pursue in the immediate), we talked more generally about how it's important to highlight the positive impacts on walking and cycling.

There's value in emphasizing relativistic value rather than explicit hypothetical numbers.

e.g. rather than implying "This exact route will now be taken for this hypothetical trip", it could be more useful to say "this segment should see reduced traffic, making it a likely candidate for someones low stress commute"

Ultimately this might just be some additional copy and some UI affordances over the existing data in ["impact mode"](#36) .

Another suggestion: Juxtapose a route from A -> B along with the improved street segments (like shown in "impact mode") to emphasize how much of the streets along this route are improved. e.g. Useful for "safe route to school" planning.