The Adventure pass is a parking pass required for parking for many hikes located in the San Gabriel Mountains and surrounding mountains. It's easily attainable and can be found at 7-11 convenient stores and Big 5 Sporting good stores. To check available locations near you that may have the pass look here.
There are two types of adventure passes, daily use and a yearly pass. The daily pass is $5 and the year pass is 30$, Additionally a second car yearly pass can be purchased for $5 which means you can have the pass for two cars for the year for $35.
To be safe, the adventure pass should be used for all roadside parking hikes in the Angeles National Forest. Plan your visits accordingly and enjoy the outdoors.