Caltrans D4 publishes draft Bay Area highway bike access map

In California, about 1,000 miles of the 4,000 miles of limited access freeway are open to bicycles according to this answer in the Caltrans FAQ section. Nobody knows the real number of miles, however, because the existing bike access maps, where they exist, are so outdated and crummy. In some cases, not even Caltrans knows where bikes are permitted. We’re forced to rely on in-depth knowledge of state law and direct observation to determine where bikes are allowed.

Caltrans District 4, which covers the nine county San Francisco Bay Area, are now developing a District 4 bike map showing where bike access is allowed within the Bay Area. They have published a draft and seek input on its accuracy from local agencies and other stakeholders.

Caltrans District 4 DRAFT bicycle map

You can view the draft D4 map here. The default map shows only the state highway system. This map shows all state routes, including those that are not limited-access freeways.

I’ve already submitted two corrections:

  • Highway 17 is open to cyclists all the way to the Highway 9 exit. The current draft shows access from the Santa Cruz County line only to the Santa Cruz Avenue exit. For northbound traffic, that’s a left hand exit.
  • State Route 82 in Sunnyvale (aka El Camino Real) now has bike lanes between Fair Oaks Ave and Sunnyvale Ave.

For Highway 17, I’m also talking about including the Old Santa Cruz Highway alternate route on this map. While bikes are legal on 17, nobody recommends riding this mountain road. I’ve rescued a couple of out-of-state tourists traveling to the coast from the Bay Area over the past few years.

To view alternate routes, you need to enable the “alternate routes” layer by clicking the layers icon (looks like a stack of books) in the upper right of the map.

“In depth legal knowledge?”

Restrictions on bike access are governed under California Vehicle Code 21960. All roads are by default open to cyclists, but authorities may close some limited access freeways to bikes. Any restriction must be clearly signed — this is why you see those “PEDESTRIANS BICYCLES MOTORIZED BICYCLES PROHIBITED” signs at every freeway entrance. If that sign is missing, bikes are permitted. You will not see a “bicycles allowed” sign in California.

Because most of our existing maps are outdated, bike advocates will drive or bike past freeway on-ramps to determine where bikes are allowed and log the information to web pages like this. These days we can use Google Streetview, too, to determine this ground truth.

Other Caltrans Districts

I think the dynamic District 4 draft map is pretty snazzy. You can zoom, pan, enable or disable layers, and search. The GIS information should be easily exportable for other uses. What do the other Caltrans districts in California offer for their freeway bike maps?

  • Caltrans District 1 bike maps are a series of large PDFs. District 1 covers northwestern California — the forest moon of Endor scenes were filmed here.
  • Caltrans District 2 cycling guide for northeastern California (published June 2008) is a pamphlet showing where bikes are allowed on I-5, as well as suggested alternate roues.
  • The District 3 bike map allows you to click through to detail maps. This draft map, published in 2004, is based on 1998 data, but the map itself seems pretty easy to use.
  • I live in Caltrans District 5, covering the Monterey Bay region and the Central Coast. The D5 bike guide, last printed in 2004, shows details maps for each county. Here’s Santa Cruz County. Can you tell where bikes are prohibited and where they’re allowed? Yeah, me neither.

    Santa Cruz County - state routes and bike access

  • Caltrans District 6 covers a big chunk of the Central Valley. Their recently published 93 page cycling guide includes a very clear overview map, along with detailed drilldowns for each county. I like it.

    Caltrans District 6 bicycle access map

  • Bike access maps are unnecessary for Caltrans District 7 (Ventura and Los Angeles Counties), and District 12 (Orange County). I’m told there are no bike-legal freeways in Orange County. In D7, I’m told the only bike legal freeway segment is on I-5 in the Grapevine.

  • The only District 8 bicycle access freeway map (covering the Inland Empire) I can find is this scan of a printed map published in 1992. There have been updates since then. I-40 across the Mojave Desert is a somewhat popular touring route.
  • District 9 (Mono and Inyo Counties publishes a bike map for each state highway in their region.
  • Caltrans District 10 (Central Valley in the vicinity of Stockton) includes bike access restrictions in their District 10 Bicycling Guide pamphlet.
  • District 11 (San Diego and Imperial Counties) includes the SANDAG interactive bike map on their bike resources web page. Purple on this map shows where bikes are allowed on freeway shoulders.


  1. The first sentence of your article says “limited access freeway”, but except for a fraction of a mile on I-280 in San Mateo County, I think all of the Bay Area bicycle access on their map is on surface streets like El Camino Real or Woodside Road or Skyline Blvd or Hwy 1 rather than “limited access” freeways. Does the 1000 mile figure really refer to limited access freeways or just to state-maintained surface streets.

  2. The one “bicycles permitted” sign I’ve ever seen is at the entrance to the Antioch Bridge (CA 160). It confused the hell out of me the first time I encountered it; I just asssumed it said the usual “prohibited” (leaving me stranded far from home) until I gave it a second look.

  3. @Kylee I was worried that this would confuse people so I’m glad you mentioned it. 1000 miles does indeed just refer to controlled access freeways, not surface streets with state highway designations. Almost all of those freeway shoulder miles will be outside of urban areas, but I have no idea who actually added those miles up

  4. It would be useful for the final map to generally show alternate routes for bike-legal but bike-unfriendly state highways, as you suggest for CA-17. In SF, riding on CA-1 (Park-Presidio / 19th Ave) or 101 (Van Ness, Lombard) would be miserable and is totally unnecessary as there are good bike routes immediately parallel.

  5. I’m glad District 4 has a nice new map. I wish District 8 would do the same, so many people, including Caltrans and CHP in that district, are unaware of what routes are legal for cyclists.

    Here’s my story of the rather unprofessional treatment I received when calling Caltrans District 8 to inquire whether there would be construction projects affecting my planned route on the I-10 shoulder:

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