How to fairly split costs on a roadtrip
June 23, 2008 9:51 PM   Subscribe

What's the fairest way to split gasoline and other costs between riders on a roadtrip?

We will travel in Japan, and there are many variables in our trip, but I imagine the same information could be used in light of the rise in gas prices in north america!

-One person will incur costs traveling by train to our start point.
-We will travel by toll road.
-We will pick one person up along the way, incurring costs when we exit from the toll road. Does that rider pay the entire cost? Is he responsible for his share of our entire toll burden, or only the cost from his point of pickup?
-Also, should all riders split gasoline evenly, or only depending on how far they travel (eg: we split gas 3 ways until we pick up our 4th rider, then split it 4 ways)?

Because I own the car, I am interested in collecting as much money as I can--I have to think about oil, wear and tear, and cleaning time. Would it be fair to split the entire cost of our trip between all the riders evenly?
posted by biwa-shu to Travel & Transportation (12 answers total) 1 user marked this as a favorite
A simple method: every time there is a cost to incur, ask the riders to cover it, and allow them to determine what is fair.

If they want to rotate, split evenly, or play rock, paper, scissors for the total doesn't matter in that case.
posted by Project F at 10:15 PM on June 23, 2008

In my opinion, I think gas cost and tolls should be split evenly between all four people. Before the trip, get your car serviced (tune up, oil change, etc.), and that should also be split between all four people.
posted by MaryDellamorte at 10:17 PM on June 23, 2008

What you could do is have everyone throw 100 bucks (or whatever, but everyone does the same amount) into a common pile, and then every time you pay for a jointly needed thing, pay for it out of that fund. If there's money left over at the end, you can either divvy it up or all go out and eat. But that way, you won't have to have the awkward shuffle and confusion of who pays for what when and who isn't paying their fair share.
posted by phunniemee at 10:30 PM on June 23, 2008

Doesn't matter if someone is picked up partway. Everyone pays the same, usually at the end after it's all totalled, and if the driver doesn't get a free lunch or two in there somewhere, at least one of the passengers is a dick.

I am a non-driver and frequent road trip passenger.
posted by ten pounds of inedita at 11:38 PM on June 23, 2008

The person who is traveling by train to the starting point should pay for their train fare themselves. Otherwise, all gas and toll costs should be split among the four participants evenly. I would not try to think of oil and wear and tear. You can't be driving that far anyway since it's just in Japan. Just accept those as normal costs of owning a car and don't pass them on to your friends.
posted by jjno at 11:43 PM on June 23, 2008

(eg: we split gas 3 ways until we pick up our 4th rider, then split it 4 ways)?

This is correct definitely for tolls and also for gas down to a reasonable granularity. (i.e. if you'll be filling up 15 times total and 10 times after picking up Guy No. 4, Guy No. 4 only pays for the 10 times. If you're only filling up two times on the whole trip, figure something else reasonable out.)

On the other hand, if Guy No. 4's costshare is insubstantial it might be reasonable to just give him a gift ride.

I speak from experience handling a road trip that involved five travelers the whole way along with four more (out of eight we met along the way) traveling some distance with us. As a protip, pick someone to hold onto the receipts for shared costs and to write the names of those sharing the cost on each receipt.
posted by TheOnlyCoolTim at 11:56 PM on June 23, 2008 [1 favorite]

Everyone pays an amount based on kilometers traveled in your car and is solely responsible for any costs they incur on their own, meaning your train-going passenger pays his/her own way, and the rate per kilometer for everyone goes down once your fourth passenger joins you mid-journey.

Estimate how much the rate per kilometer should be based on current fuel prices, road tolls, and known maintenance costs; I will assume you have car insurance to keep things simple.

For example, a trip from Los Angeles to Seattle in a 2008 Toyota Yaris tomorrow would incur the following costs:

$144.50 in gasoline, one way, according to this website
$25 for an oil change and car wash before departing
$10 for a can of quick-fix tire-puncture gel and a liter of oil
$0 road tolls

The total cost of the trip is $179.50 whether there are ten passengers or just one. The total distance of the trip is 1820 kilometers one way. Hence: $179.50/1820 km = about 10 cents a km.

That 10 cents per km must be divided between the passengers, so take the number of km traveled per person, times the cost per km, to find the amount passengers must pay.

Three passengers going the whole way, from start to end, then, would pay around $60 each for the trip. Two passengers, around $90 each.

And if a passenger were to join halfway, 910 km in? All passengers get a break and now pay less than the pre-existing ones did, as there are now more people there to share the 10 cents per km.

Math aside: the key is to make sure your co-passengers know what expectations exist before setting out...road trips can be fun but money makes people crazy and the inside of a Toyota Yaris is a bad place to have a shouting match! It might be a good idea to give them rough estimates of their costs before you all get in the car so there are fewer hurt feelings/bruised egos later. Happy travels!
posted by mdonley at 11:59 PM on June 23, 2008

Because I own the car, I am interested in collecting as much money as I can

This sounds more like business than a trip with friends. If it's business, be anal about it:

Say it's a trip of 1000 kilometers, and you have 3 people for the first half and 4 people for the second half.

Estimate the cost per kilometer, which is the total cost for gas, tune-up, etc.: c
Estimate the trip distance in kilometers: d
Cost per kilometer = c/d

For example, 500 dollars for all gas and tune-up and so on, and a total trip of 1000 kilometers, means c/d = 500/1000 = 0.50 per kilometer.

n = number of people in car (including you)

Every time n changes, restart calculations.

Say that when n = 3 (you and two passengers), you travel 500 km. For this part of the journey, each person pays 1/3 * 500 * (0.50) = 83.33

Then you pick up another traveler. With N = 4, you travel another 500 km. For this part of the journey, each person pays 1/4 * 500 * 0.50 = 62.5

A person going the full distance pays 83.33 + 62.5 = 145.83
The person going only for the last half pays 62.5

Everyone together pays 3*83.33 + 4*62.5 = 500 = c = the total cost of the trip

n = number of people in the car for that leg of the journey
c = total cost of journey (gas, etc.)
d = total distance of journey
l = distance of this leg of journey

For each leg of the trip (each change in n), each person in the car pays 1/n * l * c/d

Make a worksheet and fill in the numbers as you travel (add gas costs and so on), then do a quick calculation at the end of the trip.

But if this is friends, don't be so anal about it. Do a rough approximation and be ready to take a loss rather than come out like a pennypinching semi-friend.
posted by pracowity at 2:53 AM on June 24, 2008 [1 favorite]


Great app & site however have been having some problems with getting to it recently...
posted by puddpunk at 4:25 AM on June 24, 2008

This sounds more like business than a trip with friends. If it's business, be anal about it:

Interesting observation, and you're mostly right. It's a trip to a sports tournament with acquaintances. Some friends and some semi-friends, you might say. ;) Although I trust everyone to be fair WRT each other, I still don't want to leave it to chance and a last-minute calculation. So, like mdonley said, I'll set the rules before we set out and everyone should be happy. I'm just thinking through the best way to do it. Thanks everyone for the input!
posted by biwa-shu at 4:29 AM on June 24, 2008

I tend to favor the 'divide it all up evenly' (minus the train fare, which is none of your concern) approach.

I understand the argument that #4 owes less, but your car is in X. Your 4th passenger is in Y. Your destination is in Z. In order for #4 to get from Y to Z in your car, the car still needed to get from X to Y, regardless of how many people were in it at the time. And it's not like you can realistically find and take on a passenger who is going from X to Y to cover the cost of the fourth spot in the car that #4 isn't using yet.

Just split it all -- gas, tolls, parking, etc -- evenly at the end of the trip. If you can't afford the cash outlay for everything along the way, then let different people pay for different things, and keep track of all the expenses and who paid for them, and just even things up at the end.
posted by jacquilynne at 7:31 AM on June 24, 2008

In my past roadtrips, auto maintenance was never a consideration. The costs involved are miniscule. Just guessing, but the whole trip can't be more than 2000 km, right? Are you really going to charge your riders for a third of an oil change? Make 'em split the cost of the pint of oil you might burn? Split a car wash?? That to me, is silly. Especially if you were going to take the trip anyway, regardless of who rides with you.

The guy riding the train should pay for it himself. You don't get a discount on any other transportation for the cost of getting to it, do you?

To me, as a default, everyone else splits the gas/toll/parking costs equally. But the real answer is to decide in advance how everyone wants to split things up. (In my road tripping experience, the split was usually pretty casual- the driver provided the first and last tanks of gas, and the riders split anything in the middle. Always worked out. Or we would each put $20 in a pile and pay costs out of it, and use the remainder to buy our final meal.)

I suppose if you wanted to get hyper technical about it, you could make detailed notes of all costs and the odometer readings at each point. As well as making a calculation for the per-mile historical maintenance costs for your car. Separate the trip into legs- every time a passenger is added or removed, start a new leg. At the end of the trip, total the costs for each leg and divide those costs by the passengers involved, including charging the tolls incurred for picking up the train person. I would be surprised if this completely accurate number wasn't functionally the same as just splitting it evenly.

OR, if your passengers agree, do it this way. Determine your country's statutory per-km car rate. In the US, it's easy, because the IRS has a standard per mile rate. Then you pay all costs for the trip out of your pocket, and then "bill" each passenger per km traveled divided by total passengers for that leg of the trip.

If you REALLY wanted to start an argument, try getting paid for doing the driving...
posted by gjc at 7:46 AM on June 24, 2008

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