Air Force graduation in San Antonio TX

We will be traveling to San Antonio from Knoxville, Tennessee this summer for our oldest sons graduation from basic training. There will be 5 of us going on this 18-19 hour trip. Three of us will be driving to make it straight through, since time off from work is hard to get and flying 5 folks is expensive. I have looked at 3 possible routes that i am considering. The quickest according to mapquest and other software is down I-59 then across Texas on I-10, but i am concerned about Houston traffic. The second would take me down I-59, but cut across I-20 thru Shreveport and then around Dallas. Third is getting off interstates after Shreveport and taking the Highways and state roads through Texas and bypass Dallas and Austin all together. Myself, I would take highways and byways the entire route if time wasn't a factor, but the wife is a get there now and forget the scenery kind. With kids and others, i agree less time is a good thing being cramped in a van. Any experience or advise on Houston traffic or possibly Dallas/Austin pitfalls. We are looking to arrive in San Antonio around 5 pm. on a Wednesday.

Welcome aboard the RoadTrip America Forums!

First and foremost, you have to realize that the estimates for driving times that you get from software are fantasies. There is simply no way, short of breaking every legal restriction (such as speed limits) and physiological reality (such as the need for sleep) to attain them in reality. For starters, such estimates assume that you can drive at or above the speed limit every second and every mile. They make NO allowances for traffic, or even getting behind one semi passing another. They make NO allowance for fuel stops, meal times, or even bathroom breaks - all of which will take longer with a van load of people, especially kids, than you can do alone. They (the algorithms in the software) never get tired. They never need to take a mental health break, They never need to do anything but 'drive'. You cannot match their 'performance'. As a general rule-of-thumb, you need to add about 20% to such estimates to approach reality. In your case that means that you can expect your drive to take about 21 hours.

Now, assuming that you are OK with essentially locking the kids in a 'room' for that long, and locking yourself in there with them, you could conceivably still make this drive straight through since you have the bare minimum number of drivers required. With three adults, you can trade off the driving/navigating/sleeping chores in a rotating cycle. Note that two of those chores require that the duty officer be awake. If you can't have two adults awake at all times then you really do need to rethink this, because one of the primary duties of the 'navigator' is to make sure that the driver stays awake and alert, and to perform those services that would require the driver to take his/her attention off the road.

So, if you've gotten this far and are saying, 'yes, I can do that' then your choice of roads is the least of your difficulties. The 'back roads to miss both Houston and Dallas' option is flat out. It will simply take too long. You need ot stick to Interstate quality roads the entire way. Period. The I-40/I-30/I-35 route through Dallas is marginally shorter in both distance and estimated time. I would suggest that you get the van all packed up the night before, get a good night's sleep, and take off the next morning. that would put you in Dallas at around 3 AM the next morning when traffic should not be a problem, and in San Antonio around 7 or 8. You will be fairly exhausted and the kids will probably be cranky, and you won't be able to check into a motel for a few hours, but you should be able to arrive safe (if you follow the rules of the Speed Run

AZBuck

Thanks a lot. I am aware of the optimistic driving time guesses that the various mapping software uses. I will stick to the interstate system but must leave around 11pm to arrive around 6pm Wednesday. We want to sleep and shower before graduation activities that start at 7am! I see that all states along route are 70 mph speed limits. I always try to keep 5 above, so 75 most of the time and NO faster. No speeding tickets in 43 years and i dont want to start now, lol. If i can average 63 i should make it in 18.5 hours. The first 8 hours will be overnight with little traffic and a constant 75 mph except a stop or two for gas/snack/restroom...then after daybreak a 15 min rest area stop every 3 hours or so. Every two hours at 75 allows me a 20 minute stop to rest and still maintain 63 mph average. We are road trip veterans of many trips to Grand Canyon, Zion, and Yellowstone from Knoxville and gotten good at entertaining ourselves for long sections of highway. The kids are 15,18, and 19. Could use 4 drivers if we need to. As for shortest time, all projection i find show I-59 down to Baton Rouge then I-10 through Houston to San Antonio about 30 minutes quicker than taking I-20 over to Dallas and down I-35 to S.A. As said earlier, i have decided to leave around 11pm as to drive through Houston at around 2-2:30 and avoid rush hour traffic as best i can. Your comments and advise are as always, on this forum, top notch and very accurate.

I show a whole 3 minutes difference between going via Dallas or Houston, and I'd choose Dallas because you can easily get around the southeast side of the metroplex on I-635 and I-20. With Houston, there really isn't a decent way through or around the city.

The problem is that at 75 mph you won't average 63 mph. If you're doing extremely well, you'll do 60, and with the size of your group, 55 mph is much more likely. That's real world experience talking, not what you think your math should work out to be (which assumes a constant 75 mph average, which is just as unrealistic expectation as the computer programs)

You're also really taking a very huge risk with peoples lives by not leaving until 11pm, exactly the point when your body will be telling itself it is time to shut down for the night. For that matter, why don't you simply leave earlier in the afternoon/evening, get a few hundred miles down the road, and then stop and get some real sleep?

You can do anything you want to, but I agree with Buck completely that you are basing your plan on some very unrealistic expectations. I'll say I'd also much rather share the road with someone driving 10-15 mph over the limit and possibly getting a speeding ticket, than someone who is planning to drive more than 20 hours without real sleep, and plans to start that trip at the time when their body will be telling them they should be sleeping. You can be relatively safe while driving fast (look at crash rates on the autobahn) but when you haven't got proper rest, your body simply shuts down (compare the stats of crashes caused by drowsy drivers to those caused by drunk drivers).

We wish you the best, but strongly hope you'll reconsider your plan looking more at safety and reality, and less on when you think you need to be places.

My daily work schedule isn't your typical 9-5 job. Being awake overnight is my norm and my body wont be shutting down at 11:15 either. My oldest son traveling with me and helping drive works the overnight shift at a pilot truck stop and again this is normal hours for him also. Im trying to grasp the idea of why driving 75 wont average 63 mph with stops every couple hours. 10 hours @75mph=750 miles but if i stop 4 times for 20 minutes each time thats still 640 miles in a 10 hour period (8.5 actual driving) or 64 mph average. Ive driven the 670 miles between my house and Buffalo, Ny. hundreds of times in 24 years of marriage. I know that if i want to average 65 mph that i need to drive 73mph to account for 1 fuel stop and 2 rest area bathroom breaks and coffee. I think i will try the 40 west to Little rock and around Dallas. Maybe come back through Houston as it will be a Sunday night 9pm or so. I like different scenery, even if it is interstate roads. We plan on getting a room heading back as we will have a full day with our son and be tired. I do think safety after all. I am off the day before we leave to go down and will be well rested and have a full 8-10 hours sleep prior to pulling out at 11 pm. I myself was an aircrew member in the Air Force and am well aware that rest and preparation for a "night mission" is critical to ensure safety...

Your right, I will try that route instead. Thanks for catching that!

If you are determined to make it a straight shot, please read the Speed Run article that Buck linked at the bottom of his post. If you missed it, here it is again. Use the 3 person rotation.

Speed Run

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My daily work schedule isn't your typical 9-5 job. Being awake overnight is my norm and my body wont be shutting down at 11:15 either. My oldest son traveling with me and helping drive works the overnight shift at a pilot truck stop and again this is normal hours for him also.

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So you don't sleep in the day either when you are working nights? Same thing different times.

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Im trying to grasp the idea of why driving 75 wont average 63 mph with stops every couple hours

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If you don't increase your speed above 75mph yet you slow down as you travel through road works and because of traffic congestion you can't sustain that average. Getting to the Interstate and back off it, slowing down and building your speed for your rest breaks all chip away at your average speed. On a 'shorter' run of 640 miles and a long day on the road you can get away with 15 minute breaks and a lunch stop but on a run of over 1100 miles 15 minute breaks won't do it all the way, you will need at least 2 much longer stops to eat properly, digest, get a good break from the road and clear your mind , to refresh and let the kid's run around while.

Of course everything on paper is hypothetical and a lot will depend on 'If's' and 'But's' in the real world, whatever happens you are in for a long ride and I wish you well and hope that you enjoy your son's graduation ceremony.

Have a safe trip.

We will be safe and thank you for the concern. With 3 and possibly 4 of us taking turns driving, i will make sure 2 people are awake while 2 sleep. Wanted to make sure you understand i was hoping for 63mph AVERAGE not the 75 mph AVERAGE you keep refering to in both posts. Sometimes i will be driving 75 and sometimes driving 55 for roadwork and stopping for meals, maybe a nice breakfast at Cracker Barrell in the morning, but 63 average is very doable. I understand that traffic backs up for accidents and you just live with that. Safety first....planning on lots of sleep prior, 3 or 4 drivers, rejuvinating breaks every couple hours, and good ole common sense. Graduation is a 4 day event and this is all the time off from work we could get, but rest assured i will be prepare, rested, and SAFE! Keep posting the great advise. I did read some of your other posts on RTA forums about driving tired and the results...very interesting and TRUE. thank you, God bless.

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Wanted to make sure you understand i was hoping for 63mph AVERAGE not the 75 mph AVERAGE you keep refering to in both posts.

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Yes, I understood.

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10 hours @75mph=750 miles but if i stop 4 times for 20 minutes each time thats still 640 miles in a 10 hour period (8.5 actual driving)

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With the estimate above you are hoping to average 75mph with 'on the road time' the rest of the time you are taking a rest. I just don't see any leeway for further slow downs/delays. I know you say "if I stop" but you really should take a minimum of 2 hours for breaks in a 10 hour period with one of them being for an hour. [in my opinion of course].

It's not impossible, but I guess you are hoping for the best outcome, and we are preparing you for what is considered to be the 'average' outcome based on regular members experience who have travelled millions of miles between them.

Despite all that and not getting too carried away with averages, you should make the trip in just under 20 hours in my opinion, so lets split the difference. ;-)

Good luck.

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Wanted to make sure you understand i was hoping for 63mph AVERAGE not the 75 mph AVERAGE you keep refering to in both posts.

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We completely understand that you plan to have an average cruising speed of 75 mph, and you think that will allow you to have a total overall average of 63 mph.

We're simply telling you that based on millions of miles of experience, that's simply not likely. To have an average overall speed that high, you generally have to be cruising at closer to 85 mph, and have to be very dedicated to keeping your stops short.

We've explained a couple of times why your math is faulty, and you're basically making the same mistakes that a computer program uses. Specifically your calculations continue to assume you'll be able to travel at 75 mph for every minute you are on the highway, and going straight to zero for your stops. It ignores that there are many times where your actual travel speed will be lower, pushing your average down. For example, A 20 minute stop means at least 10 minutes where you'll be moving, but be doing significantly less than your cruising speed, as you prepare to exit, slow down for the off ramp, hit a traffic light or two, etc... (not to mention that a planned 20 minute stop is many times going to become 30 minutes when you've got a van full of people.) If things go exactly as you've planned, sure you might hit 63, but thing rarely go exactly as you plan.

In any case, your travel time will be what it will be. It looks like you're set with your plan, and we certainly wish you the best.

I don't want to beat a dead horse here, but here are some numbers from an actual trip I took a few years ago. I drove from the east side of Dallas to Lordsburg NM in one day. It was 805 miles. I got through Dallas on the freeway just after the height of morning rush hour, so the delays were very minimal. I cruised at 5 over the speed limit (verified by GPS and cruise control) all the way and hit no traffic or construction. The speed limit was 80 mph for a substantial portion of the drive, and it was 75 for the majority of the rest of the drive. The ONLY stops I made were 2 quick gas and pee stops, one pee-only stop, and a 20 minute lunch stop. It took me 13.5 hours, which works out to 59.6 mph.

You aren't going to average 63, sorry. I believe the highest speed limit you are going to encounter on your trip is 70.