It seems that many people have no idea what the various lane markings mean; lots of folks don't even know what the difference is between white and yellow lines.  So, without further ado, here are the definitions of lane markings in Texas:

	YELLOW LINES: Traffic going opposite directions is separated by yellow lines.  If you're to the left of a yellow line, and you're not intentionally passing somebody, you'd better get over to the right FAST before you see the head ornament of a Mack truck directly in front of you.  I see this confusion happen a lot when city folks get off on a rural, two-way frontage road.  There are various types of yellow lines; see below for the specifics of each.
	WHITE LINES: These separate traffic going the same direction.  There are several varieties of white lines; see below for the meanings of each.
	SOLID DOUBLE YELLOW LINES: Double yellow lines indicate that passing is not permitted (in other words, a "no passing zone".)  Even if you think you can see far enough ahead, there may be some other obstacle or reason that you can't see that makes it unsafe for you to pass.  However, it is legal to turn left across a double yellow line (see below.)
	SINGLE SOLID YELLOW LINE: This is used to mark the left edge of the roadway on a divided highway.  The use of this marking to mark the center of a two-way road is non-standard and has no official meaning.
	SOLID YELLOW LINE ON YOUR SIDE, BROKEN YELLOW LINE ON THE OTHER: You may not pass when there is a solid yellow line on your side.  Traffic on the side of the road with the broken (dashed) line is allowed to pass.  Two sets of these, with the broken lines facing each other, are used to demark two-way center left turn lanes.
	BROKEN YELLOW LINE: A single broken (dashed) yellow line means that passing is permitted in both directions.
	BROKEN DOUBLE YELLOW LINES: This marking is fairly rare and is used to separate reversible lanes. Pay attention to and obey the lane control signs or signals.
	DOUBLE WHITE LINES: Parallel white lines indicate that changing lanes or turning across the lines is prohibited.  Doing so may be dangerous or interrupt the smooth flow of traffic.
	SINGLE SOLID WHITE LINE: This is used to channelize traffic and indicates that changing lanes is discouraged, although not specifically prohibited.  You can cross it if you have to, but you should avoid it if possible.  Even a thick single white line can be crossed if necessary; however, they are really discouraging you from crossing, so you might think twice about it.  A single white line is also used simply to mark the right edge of the roadway.
	BROKEN WHITE LINE: A broken (dashed) white line separates lanes of traffic traveling in the same direction.

TURNING LEFT OVER DOUBLE-YELLOW LINES
One of the biggest misconceptions over lane markings is the meaning of the double-yellow line with regards to left turns.  A double-yellow line simply means "no passing"; it does not prohibit left turns.  In fact, you are specifically permitted by statute (italics below) to turn left over double yellow lines:

I added this section because a lot of motorists seem to be confused about the meaning of a flashing yellow signal, particularly when a regular traffic signal (red-yellow-green) is flashing yellow.  A flashing yellow signal simply means "proceed with caution", even when it's being shown by a regular traffic signal.  Most traffic signals will switch to a flash mode as a fail-safe measure if there has been a malfunction or power outage and the signal has not been reset.  Some signals also go to flash-mode during periods of low traffic.  Unbelievably, I often see people actually stop when they come upon a regular traffic signal that is flashing yellow.  You do not have to stop at a flashing yellow and indeed you shouldn't stop unless absolutely necessary because the person behind you is probably not expecting you to stop.  It would be the same as you stopping at a green light.  You only need to stop if it is a flashing red signal; in those cases, treat the signal like you would a stop sign.
 

Believe it or not, this law was just enacted in 2003.  Before that, there was no specific law on this subject.  But now there is-- if a traffic signal is out of order (that is, all of the lights are dark), then the intersection reverts to a four-way stop.  Period.  Common sense also dictates that if the signals are obviously malfunctioning (e.g. two colors on at the same time), treat the intersection as a four-way stop as well.
 

This was the most requested addition to my page before I added it.  It seems many drivers are confused or simply have no clue about the requirement to stop for school buses.  When a school bus has stopped and its red alternating lights are flashing, you must stop.  Most school buses also have a stop sign on the side near the driver that swings out, reminding you of your duty to stop.  Traffic heading in both directions is required to stop.  The only exception is if there is a physical median between you and the school bus; in that case, you can proceed, but you should do so cautiously.  Also, if you are not on the same street as the bus but on an intersecting street, you may also proceed (with caution, of course.)  And there is an exception when a bus is stopped in a loading zone on a controlled-access highway, but I have never actually seen one of these.  Note that the law specifically indicates that left turn lanes do not count as medians.  So, on a seven lane street (three lanes in each direction and a center turn lane), traffic in all seven lanes must stop for a school bus.  The requirement to stop applies in both urban as well as rural areas.

Once you have stopped, you are required to remain stopped until the lights stop flashing, the bus has started moving again, or the driver signals you to move on.

Note that in Texas traffic code, the term "highway" is defined to mean any public roadway, including city streets.  (§541.302)

Additional information
School buses are required by law to stop at all railroad crossings.  When they do this, they usually switch on their hazard flashers to warn traffic behind them of the impending stop.  You are not required to stop for the bus in this case.  You are only legally bound to stop when the alternating red lights at the top of the bus are flashing.  It should also be noted that occasionally when discharging or boarding passengers, the driver may determine that there is not a need to stop traffic and will only activate the bus' hazard flashers.  Again, in this case, you are not required to stop.  Finally, many school buses also have yellow alternating lights next to the red ones; these are used to warn drivers that the bus is about to stop.  You are not required to stop when the yellow flashers are on, but you should be prepared to stop.  Essentially, they have the same meaning as the yellow traffic signal-- a warning that the the red lights will come on shortly.

Yielding to and passing emergency vehicles

The purpose of the first law obviously is to give emergency vehicles a clear path, and the reason they need that right-of-way is also obvious.  Think of it like this: if you or a loved-one needed help and called 911, wouldn't you want everyone to make way for those emergency vehicles?

As the law says, you are required to pull-over to the right-hand side of the road and stop.  This law applies no matter which direction you are traveling relative to the emergency vehicle.  Also, needless to say, emergency vehicles have automatic right-of-way at all intersections, even if you otherwise have the right-of-way (see "Look Before Crossing Intersections" below).

The second law is fairly new (passed in 2003) and requires drivers who are approaching an emergency vehicle stopped on the road with their emergency lights flashing to do one of two things: move out of the lane nearest the emergency vehicle or slow down to 20 miles per hour below the posted speed limit (down to a minimum of 5 mph).  In other words, if you're going down the freeway in the right lane and there's an emergency vehicle parked on the right shoulder ahead, you should immediately move into the next lane to the left.  If you can't, or if you're on a road where there is no extra lane to move over to, then you must slow down to 20 mph below the posted limit.  The purpose of this law is to give emergency workers a safe area to work in when they're on or near the road.

Additional information
If you're stopped at the head of the line at a red light and an emergency vehicle with its lights flashing and siren sounding is behind you and can't get through or around the traffic, then you should first try to make room for them if at all possible by scooting over.  If that is not possible, then you should consider running the red.  The law does not specifically require or allow this, but common sense and the spirit of the law dictate that the right-of-way of the emergency vehicle takes priority over the traffic signals.  Before you go through the red, though, make sure it is absolutely safe to do so.  In most cases, cross traffic will see your predicament and stop, but if not, nudge slightly into the intersection as a signal to other drivers but wait until it is safe before you cross.  Then, go through the intersection, pull over and stop.  A safer alternative would be to turn right, but again, only when it is clear to do so.
 

You'd think most people would have enough common sense to know not to park in front of a fire hydrant, but I see it done all the time.  In case of a fire, the fire department needs to be able to find and access hydrants quickly.  If you're parked in front of it, it obstructs them and delays their response to a fire.  Would you want someone blocking the fire hydrant nearest your home if it were on fire?  (Footnote: I love the scene in Backdraft where the firefighters break the windows of a Mercedes parked in front of a hydrant and run the hose through the car.  Apparently, from the photo below, it happens in real life as well.)

Don't let this be you!
 

I get rather annoyed when I see people driving around in the dark or in bad weather with just their parking lights* on.  There's a reason they're called parking lights.  First, let's talk about the law in this situation.  The law requires you to use all your lights (including headlights) at nighttime, which is defined as being one half hour after sunset to one half hour before sunrise, as well as anytime when you cannot see clearly for 1,000 feet, which essentially covers all inclement weather as well as dusk and dawn.  Therefore, you should never be driving with just your parking lights on.  If you're in a situation where you need to have any lights on at all, then you must use your headlights. 

Some people will say that they don't want to use their headlights during bad weather or at dusk because there's enough ambient light for them to see and their headlights won't be illuminating anything.  Good drivers know, however, that headlights are not only for lighting-up the road ahead, but also they make you more visible to other drivers.  This is why motorcycles and emergency vehicles use their headlights, and is also the rationale behind daytime running lamps*.  So whenever visibility is reduced, you should use your headlights, if not to help you see but to help others see you.

Others may argue that using their headlights puts a strain on their electrical system or battery.  This is simply not true.  Your vehicle's electrical system is designed to operate all of the vehicle's electrical devices, including the headlights.  Your battery is only used to start your car and to power electrical devices in the car when the engine is not running.  When your engine is running, the alternator, which is cranked by the engine, is providing power to your vehicle as well as recharging your battery.  If using your headlights does indeed cause electrical problems for your car, then your car needs repair.

* Note that parking lights are not the same as Daytime Running Lamps.  Parking lights are when you can activate the front and rear marker lights without turning-on the headlights (see the photo below for an example.)  These are meant to make your vehicle more visible while it is parked on the side of the road, thus the term "parking lights".  To activate them, vehicles that have them typically have an interim position on the headlight switch-- position 0 is off, position 1 is the parking lights, and position 2 is the headlights.  However, parking lights are pretty much obsolete nowadays and most (if not all) recent model vehicles in the United States are no longer equipped with them.  Daytime running lamps are essentially the opposite of parking lights-- they're the headlights illuminated with the front and rear marker lights off (although some vehicles now have a separate set of lamps for the DRLs) and are generally automatically controlled.  Wikipedia has a good write-up on the differences here.
 

Parking lights
 

There seems to be a rather common misconception that if you are in a turn-only lane, you are not obliged to signal your turn.  As you can see, however, the law is quite straightforward-- you must use a turn signal any time you want to turn or change lanes.  There is no exception for turn-only lanes.  The reason is simple: while it may be obvious to you that you are in a turn-only lane, it may not be evident to motorists across the intersection or on the intersecting road.  Using your turn-signal clearly indicates to everyone that are are going to turn.
 

Imagine you are on a street approaching an intersection and there are four lanes to the right of the center marked like the illustration above.  Recently, I have seen an increasing number of people turn left from lane B and/or turn right from lane C.  Wrong!  Unless there are signs and/or lane markings indicating otherwise, you can only turn left from the far left lane and can only turn right from the far right lane (which in this example also happens to be the marked turn lanes A and D.)  If you're in lanes B or C above, you are only permitted to go straight.  If lanes A and D did not exist in the example above, then you could turn left or go straight from lane B or turn right or go straight from lane C.

OK, now that we know which lane to turn from, we need to know which lanes we can legally turn into.  In Texas, when turning right, you are required to turn both from the right lane and into the right lane unless there is an obvious safety reason not to (e.g. you're driving a long vehicle or there is a pedestrian or debris in the road.)  When turning left, however, you are permitted to turn into any lane designated for traffic headed in that direction and it is recommended that you pick the lane that interferes least with other traffic.  The exception is if you're turning left from a one-way street onto another one-way street; in that case, you must turn into the left lane.  Also, if you are turning from one of two lanes designated for the same turn movement (i.e. dual left turn lanes), then you must turn into the appropriate lane as indicated by signs and/or pavement markings.  And one final word-- keep in mind that other people may not always follow the law, so be prepared to yield if necessary, even if you're in the right.

Additional information
Good driving habits dictate that you turn into the lane nearest you.  So, if you're turning left, you should turn into the left lane, and if you're turning right, you should turn into the right lane.
 

Center turn lanes are for use only when preparing to turn left from the main road onto a side street or driveway only.  Only enter the lane just before you are ready to slow down for the turn.  Also, the Federal Highway Administration's "Read Your Road" guide (link at the bottom of this page) indicates that, when turning from a side street or driveway onto the main road, you may also use this lane as a temporary refuge to wait for traffic to clear as long as you pull into the lane and wait and don't use the center turn lane as an acceleration lane.  However, it is important to note that Texas law does not seem to specifically permit this action, and I have had reports that some folks have been cited for doing this and the court has upheld their citation, so I would recommend avoiding this maneuver unless you absolutely have to.  Finally, although section (b)(1) above says you can use the center lane for passing, keep in mind that center lanes marked as left turn lanes cannot be used for passing as the traffic signs and pavement markings indicating that the lane is for left turns only take precedence.
 

It is illegal to drive across any median.  This includes the median between the freeway and the frontage road, even when there’s a traffic jam on the freeway.  If you want to get onto the frontage road, get off at the next exit.  You’re a adult-- act like it and be patient.

Similar to driving across the median, it is also illegal to cross private property for the purpose of turning left or right from one road to another.  In other words, it's illegal to cut-through that gas station on the corner so you don't have to stop at the stop sign or red light or to avoid the line of cars waiting at the intersection.
 

This law is quite simple: if you're on the frontage road (a.k.a. access road, feeder road, service road, or gateway) of a freeway or expressway, then you must yield to traffic exiting or entering the freeway or expressway. This law covers all entrance and exit ramps, even if there are no yield signs. Even if the traffic leaving the freeway merges into a separate lane, you are still required to yield. After all, they may want to quickly move over to the right lane to turn. Note, though, that yielding does not necessarily mean stopping (see below.)
 

There's a reason for having two different signs.  "Stop" means that you must come to a complete stop, period.  "Yield", however, doesn't always mean that you have to stop.  "Yield" means that you must yield the right-of-way to other traffic by slowing or stopping as necessary.  You can satisfy the requirements to yield by just slowing down enough to let the other guy go by unmolested.  If nobody is coming, you can just keep going without slowing or stopping.  So, if you're approaching a yield sign, start looking early and if the way is clear, just keep going.  However, if it is necessary, you are indeed required to stop at a yield sign.

Additional information
Unfortunately, in city neighborhoods, it often seems that yield signs are placed where there should be stop signs, and vice-versa.  Europe overwhelmingly prefers yield signs; the US is ridiculously riddled with unnecessary stop signs.

Never, ever back-up on the freeway, even on the shoulder.  This is extremely dangerous!  Traffic is coming toward you at high-speed, and one of those drivers may need to pull off onto the shoulder suddenly or may swerve to avoid you.  If you miss your exit, just drive to the next exit, turn around, and go back.  In most cases, you'll only lose a couple of minutes.  Next time, make sure you know where you're going and pay attention to the signs.
 

Have you ever been caught in a traffic jam only to find that it was caused by a minor fender-bender blocking a lane?  Maybe you've thought to yourself, "there oughta be a law..."  Well, there is.  The law requires that anyone involved in an accident not obstruct traffic any more than is necessary.  The law even specifically requires that, if an accident occurs on a freeway or freeway ramp in a metropolitan area and all involved vehicles can be safely driven, the motorists involved must move their vehicles off of the freeway immediately.  This is to help prevent a traffic hazard and resulting congestion which, besides unnecessarily delaying others, also increases the possibility of other accidents.  Many people think that their insurance won't cover them if they move their cars from the scene before the police arrive, but this is absolutely false.  The police and insurance adjustors can determine what happened from the stories of those involved and the damage to the vehicles.  Besides, in the case of most fender-benders, you legally don't even need to have the police come to the scene.  But if you're worried, then quickly snap some pictures of the scene and vehicles with your cell phone camera before you move.
 

A common question I get, especially for newcomers to Texas, is whether it is legal to drive on the shoulder of a two-lane highway to allow other cars to pass as they have seen people doing.  The answer is yes, it is, as declared in (a)(5) above.  You'll find that most experienced drivers in Texas will automatically move onto the shoulder when a faster car comes up behind them on a two-lane road.  It's just a common courtesy and helps the other person to pass them safely.  However, there are some requirements to do this-- the shoulder must be wide enough and free of debris or stalled or parked vehicles (it is generally illegal to park on highways outside of business or residential districts).  If you do move onto the shoulder to allow someone to pass, reduce your speed a bit and keep a sharp eye out for any obstructions ahead.

You are also allowed to briefly drive on the shoulder to pass a vehicle that is slowing or has stopped in the main lane to turn left or has stalled.  Additionally, you can also drive on the shoulder to slow down to turn right, to speed up after turning onto the highway or after having stopped on the shoulder, or to avoid a collision. 

You are not allowed to drive on the shoulder to overtake another moving vehicle (except as provided above).  If the vehicle you are behind will not move onto the shoulder to allow you to pass, then you must pass them on the left.
 

U-turns

That said, many municipalities have ordinances limiting U-turns in specific areas, such as business districts, or at signalized intersections, and these restrictions are often not signed.  Check with your local police or public works department to see if there is such an ordinance in your city.

So many people are unclear as to what a yellow light really means.  By law, a yellow light is simply a warning that the light is about to change to red.  Technically, since no other direction can have a green while you have a yellow, a yellow still indicates that you have the right-of-way, and is essentially an extension of the green (but puts you on notice that the green is expiring.)  As such, you are allowed to enter the intersection when the light is yellow, and as long as you have entered the intersection before the light turns red, you have not violated the law.  Does this mean you should race to beat the red-- no, of course not.  If the light is yellow and you have not passed the "point of no return" and can safely stop, you should do so.  Note, however, that I said "safely" stop.  If the road is wet and you don't think you could reasonably stop without sliding into the intersection or perhaps having someone slide into you, then keep going-- your duty to prevent an accident is foremost.
 

Unless traffic on the freeway is completely stopped, or there is no place for you to go, do not ever stop on a freeway entrance ramp!  This is an extremely serious traffic hazard.  Drivers behind you are speeding-up to get up to freeway speed and are looking back up the freeway for a gap to merge into.  They are not expecting you to stop!  If you can't squeeze into traffic by the time you get to the end of the ramp, make sure your left turn signal is on and keep going on the shoulder until you can merge into the traffic stream.

Additional information
If you're in the right lane of a freeway and see traffic preparing to merge, move over or give them room to merge.  Although the law requires traffic entering the freeway to yield (basic right-of-way law, §545.151), good drivers will make the effort to help-out their fellow drivers.

Also, if you stop on the shoulder to change a flat tire or deal with some other emergency, and you’re ready to get back on the freeway, get up to speed on the shoulder, then signal left and merge into traffic.  Do not pull from a standing stop directly onto the freeway’s main lanes.  This very action killed a mother and van full of children west of Ft. Worth back in the mid ‘90s.
 

The issue of waiting in an intersection is a little tricky.  The law specifically prohibits stopping in an intersection.  However, subsection (f) of the same law makes an exception "if the avoidance of conflict with other traffic is necessary."  Therefore, the following sections cover the two conflicting issues regarding when to wait in an intersection.  It's amazing to me that many people do exactly the opposite of these!

DON'T BLOCK INTERSECTIONS
If the street you are on is bumper-to-bumper and you come to an intersection with a green light, remember: "Don't Block The Box!"  You should not enter an intersection if congestion would prevent you from immediately vacating the intersection when the signal turns red.  In other words, don't drive into an intersection unless you know you can get out quickly if the light turns red.  So why doesn't the exception provided by subtitle (f) apply?  In this case, you're not stopping to avoid conflicting with other traffic.  You're stopping due to congestion, which is different.  It's basically a matter of common sense and good faith in keeping with the spirit of the law.  With the left-turn rule above, assuming there is nothing obstructing the street you want to turn onto, you will be able to vacate the intersection before or immediately after your light turns red.  With congestion your egress is blocked by stopped traffic which will prevent you from being able to exit the intersection immediately when the light turns red and thus will leave you blocking the intersection for cross-traffic.

By the way, this rule can also cancel the left-turn rule above: if you have a green light, or even a green arrow, but the street you want to turn onto is backed-up to the intersection, wait behind the line until there's room for you, then turn.

New York City had such a problem with blocked intersections that they started a public education program called "Don't Block The Box!"  Obstructing intersections in this manner causes traffic on the intersecting street to also become congested.  This leads to the phenomenon known as "gridlock" where several blocks of traffic in all directions are "locked" because of obstructed intersections.

Additional information
Even if you have a green light, the law requires you to yield to traffic already in the intersection.  So if someone on the cross street was hanging-out in the intersection waiting to turn left when your signal turns green, don't roar into the intersection and pound your horn-- they're legally there and have the right to make their turn unmolested.

Before I explain this one, let me ask you this: where is the fastest water in a river?  In the middle, of course.  Why?  Because this is the place with the least friction.  This is the deepest part of the river and there are no ragged edges to slow the water.  A highway works the same way (think of it as a two-way river.)  The right lane has the most "friction": entering and exiting traffic and stalled vehicles on the shoulder.  The left lane has virtually no friction.  That is why it is reserved for faster-moving traffic.

Imagine this scenario: you're in the left lane on the freeway going faster than other traffic and you come up behind someone going a little slower than you.  Instead of waiting a few seconds for them to move over, you whip around them on the right.  At the same time, someone going much slower than you is trying to get on the freeway at the same location.  Now, both of you are creating a big hazard for each other and someone is going to have to give.  This is why (a) you shouldn't pass on the right; and (b) you should move to the right if you're traveling slower than other traffic.  The second part applies no matter how fast you are going.  Notice that the law only says that traffic moving "more slowly" than other vehicles; there is no exception given for vehicles traveling the posted speed limit.  If you're going the speed limit in the left lane and someone behind you wants to go faster, move over!  It is neither your right nor your privilege to enforce the law, and you're actually violating the law by not moving over.  You never know-- that person may have a bonafide emergency.  On the other hand, if you're the one behind the slower driver, have a little patience and give them a few seconds to move over before you zip around them.  I can't count the number of times I've seen someone in the left lane who wanted to move over but got trapped there because everyone immediately passed them on the right.  Plus, the weaving of the driver who constantly passes people causes hazards for other drivers and frequently results in "kinks" in the traffic flow.

This is one of the least-known laws.  When someone from the left lane and someone from the right lane both try to move into the same space in the center lane at the same time, who has the right-of-way?  In Texas, the law is that the person changing lanes from left to right has the right-of-way.

Additional information
Although there’s no law requiring it, you should only change one lane at a time.  If you need to get across several lanes, move over one lane, establish yourself in that lane, then move over to the next lane.  And don't forget your turn signal each time (which, by the way, is required by §545.104)!
 

This is one of my major pet peeves.  Whenever I drive downtown, I always end-up stuck behind someone on a one-way street stopped at a red light waiting to turn left onto another one-way street.  If they only knew...  A left turn on red is allowed when the street you are is one-way, and the street you are turning onto is also one-way (heading left, of course).  Makes sense if you think about it-- it's just a mirror image of a right-on-red.

However, there are some people who insist that you can make a left turn at a red light at any intersection (i.e. two-way to two-way, two-way to one-way, or one-way to two-way).  While there are some states that allow some version of this, Texas does not.  Unless both streets are one-way, you can not make a left on red.  Also, there are some who believe that you can make a left on red if there are no signs such as "LEFT TURN SIGNAL" or "LEFT ON GREEN ARROW".  Again, not in Texas.  As long as the left turn signal is obviously intended to regulate traffic turning left (which a red signal to the left of green signals for through traffic would be), then drivers are required to obey it regardless of the absence or presence of signs.  Turning left on a red light, unless both streets are one-way, is running a red light and you can be ticketed for such.
 

What is the speed limit on this curve?  Most people would say 25 mph, but the answer is that we don't have enough information to know what the speed limit is here.  The "25 mph" sign here is a speed advisory sign, not a speed limit sign.  Speed advisory signs indicate the recommended speed for a particular hazard, but they are not a legal speed limit.  Enforceable speed limits are marked by the familiar black and white SPEED LIMIT signs.  So, the speed limit for this curve would be whatever the last black and white speed limit sign indicated.

Additional information
A study by the Federal Highway Administration back in the '90s determined that the formula used to calculate the advisory speeds on curves, which was developed back in the 1930s, was significantly outdated and was producing advisory speeds that were 10-15 mph below what modern vehicles can safely handle.  Development of a new formula is now underway.  Despite that, it is a good idea to travel at about the speed indicated on these signs.  Until they're all updated sometime in the future, you could still be citied for unsafe speed if you're traveling significantly faster than what is posted, especially if you have an accident.
 

Additional information
Several people have written me saying that §545.302 does in fact prohibit changing lanes in an intersection.  However, they are incorrectly interpreting the statute.  Here is the text of that statute:

Notice that the statute specifically says "an operator may not drive to the left side of the roadway".  This is different than the changing lanes discussed above.  "Changing lanes" is when there are two or more lanes for the direction you are traveling and you wish to change between those lanes.  "Driving to the left side of the roadway" is just that-- going across the yellow line down the middle of the roadway and crossing into oncoming traffic.  As you can see by the statute, doing this is illegal within 100 feet of the approach of an intersection.  My guess is many people misconstrue or misremember this rule to mean you can't change lanes at an intersection.  However, the two are completely separate things and there is no restriction on changing lanes.