Small & Hidden Facts About Our Interstates

By A. H. Bosley

Some of this information is, or should I say was, hard to explain so please bear with me. Also, this article was inspired for a newer driver as my nephew starts his career in trucking. I’m so excited for him!


On each and every one of our interstate highways there are mile markers on the side of the road;
From mm 0, West end of the state, and they go up as you head East.
Then from mm 0, South end of the state, and they go up as you head to the North.
So: On I-95 Florida (South-North), Miami = mm 0 and N. Jacksonville is mm 360.

Thus, (West-East) on I-10 in Florida, there is Spanish Fort, mm 0 and Jacksonville is mm 360. (It is a coincident that the mm are the same in Jacksonville on two different interstates.) This is true for every state except one that I know of, and this is California. These are posted in most states, every tenth of a mile. It is usually a green, vertical sign and will state the mm number, and under that number is the tenth. Such as: mile marker 184 over 7. This lets you know the exact location on the road.

Most states exit numbers coincide with the mile marker location, but not all. Such as New York – but this is easy to figure out, just check your mile markers to your exits as you enter each state, and continue to check periodically.

Now, California is one of the states that falls into this category. California’s mm run from county to county on each interstate with it’s West/South ends starting over at zero. You will learn what states do and don’t as you get more experience. Some state roads in California run with the mile markers. Also, the mile markers in CA are noted on a white vertical rectangle that is very close to the ground, and the black numeric value is horizontal and very hard to see and to read.


Just a tid bit, but:
Tractor trailers should be cautious when seeing the word parkways, as most are NO TRUCKS ALLOWED.

Interstates run in consecutive order. West coast lowest going higher in numbers as you head East.
• I-5 California Coast
• I-95 Florida Coast
• I-94 Northern-most Interstate
• I-4 Southern-most Interstate

Numbers run from West to East as do your mile markers, and from South to North.
• All odd numbered interstates run North and South
• All even numbered interstates run East and West

Sometimes they don’t appear to be running in the correct direction, such as I-4 in Florida. It looks like it runs more North and South, but it is still considered an East/West interstate. Then again, I-81 around Virginia and Tennessee in runs more East and West in that area but it is a North/South interstate. Some criss-cross, and thus are out of sequence but the general rule applies.


A & B Exits
Off a North/Southbound interstate. (Odd Numbered)
• A usually heads East
• B usually heads West

Off an East/Westbound interstate. (Even Numbered)
• A usually heads South
• B usually heads North

MOST OF THE TIME. Please check as different counties may not follow this rule.

Texas doesn’t follow this simple rule at all. Be careful, pay attention, and this too you shall learn in terms of what areas you can trust to follow these rules and where you can not.

Some exits have C, D & E. – I have no clue here.
If there is a rule on this I have not figured it out as of yet. Let me know if you do.

Exit Signs
Most signs have the exit number on the top and right-hand side of the sign, this is telling you it is a right-hand exit. If it is on the top left then it SHOULD be a left-hand exit. Some run right across in the middle of the sign, and usually means a right-hand exit as well. As always, there is the chance that the signage doesn’t follow the rule so it is up to you to make sure. It is only a hint, as NO rule is not set in stone.

Lines On The Interstate
There is usually a solid yellow line on the far left of the travel lane. This indicates that any other lane beyond that line is headed in the opposite direction, thus, do not cross. Then you have the white dotted line (the zipper) which indicates lane bounties. Then there is the solid white line which indicates the far right side of the travel lane and the beginning of the road’s right shoulder.

When you see solid white lines and they are indicating travel lanes, (usually seen in construction zones) the solid lines indicates DO NOT CHANGE LANES.

Then you will see a normal dotted line (zipper) change, getting smaller and closer together. In most cases, this indicates that you are LOSING the lane. Finally, there is the large, fat dotted line in the far left lane that normally will have a triangle in it, or a sign that reads ‘HVO.’ Meaning: ‘High Vehicle Occupancy’ – NO TRUCKS ALLOWED, no matter how many people are in your tractor. This is for carpooling, and must have a minimum of two people to use this lane in a for wheeler. Definitely NO SEMIS! Must people who drive cars (4-wheelers) do not adhere to the ‘Do Not Pass,’ or ‘Do Not Change Lane’ indicators, whether posted in writing or any other way indicated, so as always use caution.

Remember not all of these rules apply all the time, and as the driver, it is YOUR RESPONSIBILITY to make sure you know where you are going by reading your map ahead of time. Any well-thought-out travel plan will save you undue headaches for sure. Know where your turns are, I.E. exit number, state, town etc. When I first started, I wrote the route I was taking down. Everyone has a system when going into a new area. The only preparation method that I DON’T feel is good, is following your GPS. DO NOT FOLLOW IT BLINDLY! It is only one tool, and one that is least reliable, especially for a truck. Car GPS’s should never be used as a route planner. Use your map first, know your route. Have a backup plan when necessary. Call your shipper or consignee for directions into the facility. Ask specifically for tractor-trailer directions. The receptionist may give you the route she takes every day, which wouldn’t work as well for you. So ask for the shipping and receiving department first!

As always, never drive behind a backing truck. Always turn your headlights OFF, then on when helping a trucker get back over in front of you. NEVER EVER USE YOUR HIGH BEAMS. Do nothing at all if you are opposed to turning off your headlights. High beams are never good to signal anyone at night. You’re just taking away their night vision, and this is the reason we turn off the lights to begin with. The trucker looks in his mirror and can clearly see FOR HIMSELF he is clear to come over.

Use your flashers (HAZARDS) when climbing a hill and lost your speed, at around 45 mph – or anytime something is abnormal around you. It brings attention to others behind you that; traffic has slowed or is stopping/stopped.

Please be safe out there! Don’t worry if you feel you are going to slow around curves or construction zones. Everyone started somewhere, at some time, in someone else’s truck. Be safe, be open to learning from everyone. Pick out the good stuff, and leave the rest behind. Help out a fellow trucker when possible, and don’t take everything out on the road to heart.

Trucking is not just a profession, it’s a way of life.