California Vehicle Code (VC) § 21460 makes it illegal to drive to the left of a double solid yellow line. However, the law also provides some exceptions. Double yellow lines are usually painted on the road, but the law permits raised pavement markers to be used to indicate double lines.
In California, you can cross a double yellow line in these situations:
To pass a slower vehicle – broken line on your side. If the double yellow line closest to you is broken (dashed), you may cross them to pass another vehicle. (VC 21460(c)(1).) Do not cross over the lines to pass if the line is solid on your side.
To make a left or U-turn – broken lines on the inside. If two double yellow lines that are broken on the inside create a turning lane between opposite lanes of traffic, you may use that center lane to make a U-turn or turn left, provided that you follow any other visible signs. Be aware that this type of lane is often used as a turn lane for both directions of traffic, and often arrows are used to indicate where your side is permitted to turn. You can also make a left turn into this center lane to help you merge into traffic to your right. Whether making a left turn from this lane or into this lane, you can travel between the double yellow lines for a maximum of 200 feet. (VC § 21460.5.)
To turn into or out of a private driveway. You may cross a double yellow line to turn into or out of a private driveway. (VC 21460(d)(1).) For example, if you live on a street that is divided by a double yellow line, you may turn into your driveway across the double lines.
To make a legal U-turn. In some circumstances, you can cross a double yellow line to make a U-turn. For example, if you're in neither a business district nor a residential district, you can cross a double yellow line to make a U-turn as long as you have an unobstructed view for 200 feet. Learn more about U-turns in California.
To get out of the way of an emergency vehicle. If you're traveling in a carpool lane marked by a double yellow line, you may not exit the lane until the line becomes broken. However, if an emergency vehicle comes up behind you, you must safely cross the double lines to get out of the lane to allow the emergency vehicle to pass. (VC § 21655.8.(b).)
If a law enforcement officer catches you illegally crossing over a double yellow line, you will likely get a ticket and face a hefty fine. You may also receive points on your driver's license for the moving violation. If you cause an accident after illegally crossing a double yellow line, the consequences will be more severe -- you could become financially liable for the other driver's damages and injuries.
If believe that you were wrongly ticketed for illegally crossing a double yellow line, you may be able to fight your ticket yourself. However, if the incident resulted in an accident, or if you also received other violations – such as DUI or reckless driving – get help from a lawyer who can help you to understand your options and present your best defense in court.
For in depth information about how to fight your ticket, read Fight Your Ticket & Win in California, by David W. Brown (Nolo).