I wrote this mod after watching Katherine of Sky frequently hand-set her running speed using the console during her Whistle Stop Factory series.. It simply rotates the value of player.character_running_speed_modifier between one of three different (configurable) values in response to a keypress. A small floating indicator of which value was set appears over the character's head when this is done.

There is another mod that is incompatible with this one, but does everything it does and more. It might be a bit harder on the UPS though. That mod is Kuxynator's Running Mod

This is not compatible with other mods that set this, most notably the 'Progressive Running' mod.

This is a cheat, but it's a quality of life cheat, and not necessarily game breaking, though it does greatly reduce the utility of cars. This is useful so that you can have a ridiculous run speed for speeding across the map, but then easily slow back down again when you want to work on a specific part of your factory.

I have this on GitHub, but I'm a Mercurial user, so its real home is https://osdn.net/users/omnifarious/pf/RunSpeedToggle

Additionally, I will pay attention to bug reports on the mod portal, especially since Wube has added support for notifications. And if you're having a problem, I would greatly appreciate a bug report. :-)

If you're interested in this mod, you might want to check out https://mods.factorio.com/mod/tackleautorun - I haven't checked for compatibility yet, so they might not work together. But I suspect that they will.