What's the difference between a solid white line and a double solid white line on the United States?

I read on https://www.wwinjurylaw.com/blog/2016/november/can-i-cross-over-the-solid-double-white-lines-ne/

California Vehicle Code Section 21460 (b): Double white lines. (b) If double parallel solid white lines are in place, a person driving a vehicle shall not cross any part of those double solid white lines, except as permitted in this section or Section 21655.8.

That sounds the same as a single solid white line to me. I'm mostly interested in California.

  • 1
    I think you mean "line," not "lane."
    – phoog
    Commented Sep 16, 2019 at 2:36
  • @phoog thanks, fixed! Commented Sep 16, 2019 at 2:38

1 Answer 1


The article to which you link, which describes the solid lines, mentions the Manual on Uniform Traffic Control Devices (MUTCD).

This document describes the standards used nationwide. States were required to adopt these standards by 2012. Your linked article also mentions that California is changing their double yellow lines separating HOV lanes to double white lines in order to conform to this standard.

From the MUTCD Chapter 3B - Pavement and Curb Markings:

When used, lane line pavement markings delineating the separation of traffic lanes that have the same direction of travel shall be white.

Later in that section, describing the use of single and double lines (emphasis mine):

Where crossing the lane line markings is discouraged, the lane line markings shall consist of a normal or wide solid white line.

Where crossing the lane line markings is prohibited, the lane line markings shall consist of a double white line.

The California driver's handbook describes where those lines are used:

Solid white lines mark traffic lanes going in the same direction, such as one-way streets.

Double white lines are two solid lines that indicate a lane barrier between a regular use and a preferential use lane, such as a carpool/HOV. Never change lanes while in these lanes; wait until a single broken white line appears. You may also see these parallel lines in or near freeway on and off ramps.

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