From Halopedia, the Halo wiki
How Pedestrian is an achievement in Halo: Combat Evolved Anniversary and Halo: The Master Chief Collection. It is awarded for completing the campaign level Halo on any difficulty without entering a vehicle. It is represented by a white M12 LRV "Warthog" over the MJOLNIR Mark IV helmet in the original game, and a screenshot of Ice Fields in The Master Chief Collection.
The achievement is worth 25 Gamerscore in the original game; in The Master Chief Collection it is only worth 10 points.
- The name of this achievement is most likely a reference to an episode in the A Different Way to Campaign series on Halo Waypoint named "The Pedestrian" hosted by Jeremy Patenaude. A Pedestrian, explained by Patenaude, is a player who walks during a part of the campaign level that needs the player to commandeer a vehicle, which fits the requirements of the achievement.
- The method that is required to unlock this achievement is similar to that of the "They've Always Been Faster" achievement in Halo: Reach.
- To unlock this achievement, the player must grenade jump over a large gap near the beginning of the underground tunnel section.