I've done both. Growing up in the 70's we drove from Seattle. That's about 20+ hours of driving each way or about 1.5 days each way. That was back when the disparity between gas costs and airline tickets was much much wider.
The primary consideration for *most* people is basically cost in terms of money, time, and hassle. With money the most important followed by time, then hassle. This is what *most* people consider when making a decision on *average*.
We wouldn't ever consider driving for three reasons: a) too costly in money because of gas and depreciation of the fairly new and expensive cars we own, b) too costly in time taking up 3 full days of our vacation that we'd prefer to be sitting by the pool or riding the rides, and c) safety factor which is often overlooked with almost all drivers. I'll write more about that later.
Again there's not a formula that can be blindly applied to everyone but here's food for thought on why we make the decision to fly.
Now with a family of 4, an easy simple way to determine driving costs is the current 2008 IRS business write-off rate of $0.58 a mile. You could determine your MPG times the miles times the price of gas, then add in depreciation costs on putting all those miles on your car (wear and tear on brakes, tires, engine, etc), then add in the cost of meals along the drive. Then add in your lost cost of opportunity unless you really enjoy sitting in the car for 20 hours and have fairly limitless vacation time, then the lost cost of opportunity is $0 for you. if you'd rather be doing something else, say swimming at a water park or riding a ride, and have say only a week for the vacation, then put an arbitrary number on what doing something more fun than riding in a car is worth to you if you could pay to do that instead, say $5 or $10/hr? It could also be vice versa. If you are terrified of flying determine how much per hour of flight you would pay to not fly and factor that as a negative hourly rate like -$10/hr times the flight time.
Even if you set your lost opportunity cost to $0 assuming you like road trips, but aren't terrified of flying either, from Seattle to Anaheim is 1,163 miles. Let's say a minivan that gets decent gas mileage of 25 MPG on the freeway and you're looking at 93 gallons of gas X $3.75 gallon = $350 in gas. Let's say the 2,300 miles you put on the car costs in depreciation and wear and tear about $0.10 a mile which is a little over $1000. This comes out to a total of $1350. This doesn't including meals for the 3 total days you are on the road or a hotel room for the night.
Most people will have difficulty grasping and acknowledging the whole depreciation, wear & tear aspect since it is something that is not easily observed in a short period of time. They just look at the immediate costs driving the vehicle that far. It's not like you will have to immediately get a brake job, tune up, and 4 new tires right after your trip. It also matters whether your vehicle is newer (under 20,000 miles) or older (over 80,000 miles) as the amount of depreciation slows with age. That's why I recommend just using the IRS write-off rate of currently $0.58 because that rate reflects the IRS's calculations on the average cost per mile of driving an average car. Using this calculation $0.58 X 2,300 miles = $1334... gee about right on $1350. It may be overkill for some circumstances, or too conservative for others, like if you are driving an Escalade on premium gas the whole way versus a Toyota Camry with 100,000 miles on it.
Figure $20 for some fast food for 4 for 4-5 meals plus $60 for a cheap hotel room each way, you've then got about $300 in motel and meal costs on the road. So even if we figured the mileage rate was too high and was closer to $1000 instead of $1350, it still comes out to about $1300 including motels and meals on the road. (Just gas, motel, and meals alone is $750).
Let's look at someone who loves road trips and hates the hassle of the whole airport process. Lets say including baggage checkin-in/pick-up, security and waiting + flight time, the total airport+flight time is 5 hrs each way or 10 hrs and you'd say $10/hr per person to AVOID flying so -$40 X 10 hrs = -$400 and you have an old Honda sedan that gets good gas mileage so + $1000 in gas and depreciation/wear+tear instead of $1350 less thr $400 to not fly = $600 cost.
If you put a lost cost of opportunity of $10/person per hour of driving that's $40 X 40 = $1600 + $1350 = $2950. So the cost of driving 2300 miles to DLR could be as little as $600 or as much as $2950 depending on how you figure it, all things considered. The average of those two figures would be $1775. Pretty amazing.
We got 4 tickets to Orange County for $225 a piece. We fly a lot so the airport process is always smooth and quick, arriving 1 hr before the flight. We stay within walking distance of the DLR gate so we don't need a rental car. So total cost from Seattle to
Disneyland is $900 + taxi to/from Orange County airport (relatives drive us to/from SeaTac.) So even if we said we are neutral about long roadtrips, the decision is an easy one for us - $950 or so in travel costs and 3 extra days of playing at the resort, or $1350 and 3 less days to play at the resort.
Now if you live closer, like anywhere in Cal, Nevada, or Arizona and have a blast on roadtrips, then driving would be more of a viable option.
After having done both several times, from Seattle. I can say I like flying much better, even if cost was cheap and driving cost half as much as flying, I prefer to spend the three days by the pool rather than in the car. Not that I've really enjoyed the road trips too! I've already seen just about everything there is to see in WA, OR, and CA and we play the same games and such in the condo or hotel room that we can play in the car.
I'd say we'd have to be within 8 hrs drive to make it not worth going through the airport and flying into Orange County. That would be cities within 500 miles of Anaheim.
Other considerations, if you have a family larger than 4, the total airfare cost could become more prohibitive obviously.
The last word is on safety. Most people, have the irrational belief that driving is much safer than flying. The pure and simple fact it is that it is not, in fact it doesn't even come close to the safety of flying. This is somewhat counterintuitive because airline accidents usually result in fatalities and car accidents do not. Plus the fact with cars you feel more in control because you are driving - but, you aren't driving all the thousands of other cars on the road that you will be passing or that will be passing you.
First we need to agree on the terminology. Safe means without accidents that result in economic loss, bodily injury, or fatality.
In the US, each year there are about 40,000 deaths per year in automobile accidents vs. about 200 in air transport. To put this in perspective, the chance of dying in an automobile accident is about 1000 times more than winning a typical state lottery in a year.
Even if we ignore property and bodily damage (there are many more car accidents that result in injuries and not death) and focus on fatalities only, we should look at fatality rates per passenger mile traveled. This require some research. You can go to the National Transportation Safety board website
(
http://www.itsasafety.org) to do some research or look at a summary table here (
http://hazmat.dot.gov/riskcompare.htm). According to the latter, each year in the US 1 out of 6800 drivers dies in an auto accident. The rate for airline passengers is 1 in 1.6 million. The same table shows that per passenger mile, air travel is safer by more than a factor of two. I doubt this last figure; I think it should be about 100x safer, because I guess we drive and fly the same number of miles (give or take a factor or 2-5) per year, yet fatalities are 200 times higher for autos than for airlines. It's more about the exposure time to the risk. With flying you are only exposing yourself to death or injury about 1/10th the time you are when driving since flying is 10 times faster for any given distance.
So for me personally, if I have the money, I'll fly even if it is more costly than driving because it is quicker, giving me more vacation time at the destination, and a lot safer. But that's just me.