Category: Legislative (LRN)

CARxR 1.07: Highway Numbering: State Highways and Post MilesCARxR 1.07: Highway Numbering: State Highways and Post Miles

In this episode, we explore numbering systems in state highways. It is the start of a four part miniseries on highway numbers in California. Specifically, this episode explores the rhymes and reason for the assigning of signed route numbers to highways with the state shield. This includes looking at the patterns in those numbers, and how the numbering system stands today after the Great Nenumbering. The subsequent episodes in the miniseries will explore the numbering system of US Highways, the numbering of and the history of California’s Interstates, and the signed county route system.

The episode also explores another numbering system on state highways: Post Miles. As opposed to sequential mileage numbers as is found in other states, California uses a system called post miles that identifies points along a highway using a combination of a county and a mile point from the southern/western county line, possibly with clarifying prefixes or suffixes. We discuss this system is good detail.

Our interview is with Andy Richardson, who retired from Caltrans as a Subject Matter Expert in Geographical Information Systems, Linear Referencing Systems, and Postmiles. Andy worked as a GIS specialist for the State of California since 1988, including Caltrans between 2001 and his retirement in 2021. In his last years at Caltrans, he implemented the Department’s current Linear Referencing System.

Here are some relevant links (I may edit this to add more links in later):

Here’s the link to the show:

And here’s the link on Anchor.FM:

Episode 1.08 will continue the numbering miniseries, and we’ll be looking at numbers on the US Highway system (black and white shields): what are the numbering patterns and algorithms, and how route numbers are approved. We’ll also look at the history of US highways in the state. Looking forward, Episode 1.09 will explore Interstate numbering and all things Interstate; and 1.10, will look at the County Sign Route system. As always, we’re looking for interviews for future episodes. If you have any leads, please contact us:

  • For 1.08: Someone familiar with AASHTO’s role in highway numbering.
  • For 1.10: Someone familiar with the county sign route system, either from the Caltrans office that coordinates the program or the a county Public Works person.

We encourage you to explore our back catalog through this site or our Anchor.FM home.

Episode 1.02: Building a State Highway System: The 1920sEpisode 1.02: Building a State Highway System: The 1920s

This first season of California Highways: Route by Route establishes the background listeners will need for our subsequent route by route podcasts. We’re starting with a history of the state highway system. In Episode 1.01, we discussed how the highway system started and got through the first three bond acts that created a large number of today’s routes. This second episode explores the 1920s: the start of the gas tax, the Melville Act that allowed the state to take over traversable highways through small cities that cannot afford them, as opposed to just rural highways between cities, the impact of the Breed Bill, and the establishment of the Division of Highways (today’s Caltrans). We’ll go over some of the major highways added during this time period, and most importantly, we’ll discuss the start of the Federal Highway system, better known today as the US Highways. We’ve got a special interview related to that subject: Joel Windmiller, President of the California Chapter of the Lincoln Highway Association.

Here are some relevant links:

Here’s the link to the show:

Here’s a link to the show on

We welcome your comments on the episode. We’re also looking for someone to donate or provide more appropriate theme music.

We’re looking for interviews for the remaining set of Season 1 episodes, as indicated. If you’ve got a lead on a speaker, please let me know.

  • 1.04: Building a State Highway System: Expanding the System: Someone to talk on the 1956 Interstate Highway Bill
  • 1.05: Building a State Highway System: The Great Renumbering and New Freeways: Someone to talk on the construction boom of the 1960s and/or the impact of the great renumbering.
  • 1.06: Building a State Highway System: CEPA and Reality: Someone to talk on the impact of budget cuts and the California EPA/EQA on highway construction
  • 1.07: Highway Numbering: State Highways: Someone to talk on how the state numbers state highways — in particular, anything official on numbering patterns, or the rules for signing things.
  • 1.08: Highway Numbering: US Highways: Here I’d like someone to talk on the role of AASHTO on numbering US highways
  • 1.09: Highway Numbering: Interstates: This is Interstate numbering, so again an expert on Interstates — either numbering, the federal aid highway acts, or the chargeable/non-chargeable distinction
  • 1.10: Highway Numbering: County Routes: This is numbering of county highways, so anyone from a county public works department on the signed route system
  • 1.11: The Naming of Highways: A state legislator on highway naming resolutions
  • 1.12: The Organizations of State Highways: Someone from the California Transportation Commission on the role of the commission.