M & M 3E allows an athletic test as a free action to add a range to its speed in that round, effectively doubling its speed.
You can take a DC 15 track and field test as a free action to run faster: one or more degrees of success increases your forward speed range by +1 in a round.
It is a good way to let players accelerate when they need to increase speed, but my players have realized that, like the Stunt test to climb Prone as a free action, there is no problem integrated into the system for try It's every time you're lucky.
Is there a good way to balance it so that there is some risk, but not enough so that players never take advantage of it?
I considered raising the 2E configuration for All-Out-Movement and only allowing a total number of rounds equal to the Constitution (Resistance in 3E) before you start having to perform Fatigue checks, but that still allows a lot to run. and since it is often intermittent, I suspect that they will probably try to argue that they rested while running among them.
Another option would be to provide a consequence if they lose the check for more than one degree of failure, but some of them have bonuses (or skill mastery) high enough to never happen.
Or is this something that is probably best handled in the character, since it is difficult to be stealthy while running, and / or people who look at them strangely by entering from time to time in a sprint?