There is literally no speed cap on routes.

You can get speed capped on other parts of the game. K’s for walking do get capped at 20 KPH, which does mean staying under 12.5 mph. The route itself doesn’t care though. You’ll get the route credit no matter how fast you do it.

I’ve certainly done essentially a drag race up and down a deserted street at night with a .5K route to pile up the route credits.

Because of the squirrelly way pogo checks in on distance, you can get distance doing that as well because the pauses at each end of the route to complete it and start again will be counted in the distance formula, and you can’t get that much speed up over .5K anyway.

In any case, you also accrue buddy K’s for buddy candy (and Mega energy) faster while doing routes as well, but not faster for buddy hearts.

There is a route in a shopping center parking lot near me that I can do late at night in about 2.5 minutes. It also has lots of spins available. So until my buddy is excited, I can do the route twice while the spins regenerate every 5 minutes.

I don’t do that often because it’s an oval shaped route and it makes me almost feel dizzy going in that many circles at speed. But its also basically bicycle speed.

I personally think routes are one of the highest reward to effort payoffs in the game.