Slow Ramp is one of the many obstacles in Battle Run. It can be of any various lengths.
When running upon, a character is slowed. The slow can be mitagated with Boost or any other Weapon or Pet that gives a speed boost. Similar to the Speed Ramp, if you jump over it, it does not slow you. The slow does not fade right away, and rather it fades over a period of time, depending on acceleration.
Slow Ramp should be avoided whenever possible. However, you have to be careful: Often, you only have two things you can do: Take the Slow Ramp, or jump into Spikes/Fire. In which case, take the Slow Ramp. Using a pet like Spider or Caterpooper in these situations can make a certain slow ramp almost impassable.
It's counterpart is the Speed Ramp.