Chain controls on the Grapevine and Tehachapi, explained
Caltrans posts three chain control levels on California mountain highways. The verdicts on this site show the live level for each corridor in the state's own terms. Here is what each level requires of your vehicle, quoted from Caltrans' published definitions.
R1: chains, traction devices, or snow tires are required on the drive axle
R2: chains are required, except on four wheel and all wheel drive vehicles with snow tires on all four wheels
R3: chains are required on all vehicles, no exceptions
How the two passes differ
On the Grapevine, control runs through fixed checkpoints. Caltrans' chain control feed lists two on I-5: one at Grapevine, near Lebec on the Kern County side, and one at the Los Angeles and Kern county line. When a level posts, the level at those checkpoints is what this site's Grapevine verdict reports, and the CHP staffs the points to check vehicles.
On SR-58 the same law applies with no fixed stations in the published feed. Tehachapi controls post for the mountain segment between Edison and Mojave when a storm demands it, announced on QuickMap and the overhead signs. This site watches both sources, and the Tehachapi pages say plainly that there is no checkpoint to read, rather than pretending a station exists.
Speed under chain control is capped by conditions and by the posted chain control speed, typically 25 to 30 miles per hour. Chains go on the drive wheels; on a towed trailer, the braking axle chains. And on both passes the oldest rule in the mountains applies: if you are asking whether you need them, carry them.
Check the live level before you go
Questions drivers ask
Where are the chain checkpoints on the Grapevine?
In the Caltrans chain control feed, I-5 has two published checkpoints: at Grapevine near Lebec and at the LA and Kern county line. When control is posted, those are the points where the CHP checks vehicles. This site's Grapevine verdict reads their live status.
Are there chain checkpoints on SR-58 over Tehachapi?
Caltrans publishes no fixed chain control stations on SR-58. Controls there are posted for the mountain segment as conditions require and announced through QuickMap, the overhead message signs, and the CHP. This site mirrors the signs and the feed, so a posting appears in the Tehachapi verdict when the state publishes it.
Do I have to carry chains even when no control is posted?
In California chain control areas during winter, yes, the expectation to carry chains applies, and the CHP can require them at a checkpoint the moment control posts. Storms on both passes can post controls faster than a driver can buy chains, which is why every winter page on this site says carry them.
Does four wheel drive exempt me from chains?
Only at R1 and R2, and only with snow tread tires on all four wheels as the definitions state. At R3 there are no exceptions: every vehicle chains up. Read the level in the verdict, not the badge on the vehicle.