Adult 1-Day Pass $6 /$12 Premium Regional
What does "Premium Regional" stand for, and how is the premium regional fare different from the standard fare?
On this page it explains that some services require a "Premium Pass"
Trips that include the COASTER or Rapid Express require a Premium Regional Day Pass
I'm picking that the standard Regional Pass does not include the COASTER or Rapid Express.
Additionally, from this page
What is the difference between the Regional and Premium Regional passes?
The Regional Day/Monthly/30-Day passes are valid on most MTS and NCTD bus and trolley/SPRINTER services. The Premium Regional Day pass also includes travel on the MTS Rapid Express/Premium routes 280/290 and NCTD Flex (except 372). The Premium Regional Monthly/30-Day pass also includes the MTS Rapid Express/Premium routes 280/290 and the rural services. There are no upgrades from the Regional Pass for the rural/premium service.