Car odomoter vs Google map distances?

We have a nanny who picks up our kids after school and drives them around to their various after-school activities each day. She uses her own car, and we have agreed to reimburse her for her mileage using a standard rate. To save the time and effort of her having to keep a detailed log using her car’s odometer, I have been estimating her travel distance using Google Maps. Today the nanny complained that the Google numbers are wrong and that the actual distances according to her odometer (when she has checked) are higher.

This raises the question, how accurate are the estimates of distance of Google compared to the odometer in a car? FWIW, her car is a low-end Honda that is probably more than 10 years old. And I don’t think there is much of a question of routes as it is pretty clear in most cases which is the shortest route to take.

I can’t find any sort of statement by Google speaking to the accuracy (or lack) of their distances.

I only pay close attention I’m on long trips - knowing, for example, my exit is 14.4 miles away and then using my odometer for reference. It’s always been quite accurate.

City driving is probably a different story, especially in aggregate. There’s a lot more non-optimal movement as compared to the straight lines of the highway. Plus, the shortest route isn’t always the best route depending on traffic, construction, etc.

IIRC, manufacturers only need to make speedometers (and thus odometers) accurate within +/- 5%. They frequently err on the high side, so that their customers don’t get a lot of speeding tickets (and if you want to get conspiratorial, to slightly reduce warranty coverage…) On top of that, if the car has slightly smaller tires than the original, the odometer will read even higher.

I’d expect Google’s directions to be pretty accurate. After all, they have enormous amounts of map data for the entire world, built from many different sources.

How much higher is she claiming? 5% is plausible, 10% is a stretch but isn’t crazy. And in absolute terms, that’s probably on the order of a few miles per trip, which works out to be a buck or two. If that’s all it is, I wouldn’t bother quibbling.

More than that and she’s either taking longer routes, including side trips inadvertently, or trying to squeeze extra money out of you.

Perhaps she likes to take less traveled routes, not unreasonable especially considering her job and plenty of people do. To make it easy perhaps she will accept a standard google distance + a certain percentage to allow for non-straight line travel.

It’s possible that she is taking an indirect route, but I had asked her to take the most direct route for exactly these reasons.

I am paying her about $1.15 per mile, and it comes to about $300 per month. So I am not that keen to pad the rate even further.

My view is that as long as Google is accurate, that would be an easy standard for us to agree to, and not have to include the uncertainty and nuisance of keeping track of the actual number of miles.

That is an incredibly generous rate. For that money, your nanny shouldn’t be complaining about a percentage difference.

You could just tell her she’s welcome to keep a log of her own and you’ll reimburse her at the standard business rate, which is 53.5 cents/mile.

Less aggressively, you could both agree on a fixed reimbursement per month and she can pick any routes she wants.

Sorry, I should have made it clear that it is the equivalent of $1.15 per mile. I am in Switzerland and the current going rate is CHF 0.73/km.

But yes, I also feel that is pretty generous, given that the cost of fuel is only about 0.20/km. But even when you take into account maintenance, depreciation, tax, and insurance, I am pretty sure she is making a profit…

She should be; she’s performing work for you.

sorry? I don’t understand

Asking someone to take the most direct route is perhaps not the best tactic, many people don’t like this level of micromanagement, will be dissatisfied to a certain extent, yes you may save a bit but may have to some level a resentful employee. You may be changing a very pleasant aspect of the job and crushing it and replacing it with something that is dreaded instead. Be careful when takign away employee freedom.

Taking away the incentive to take a more scenic route for extra money would be a better way IMHO, let him/her make the routing decision (as long is it’s not eating up too much time, but if she takes the kids it appears the scenic route may be better for them), but agree to pay in google miles (and perhaps you have to give in a bit here and up that rate so everyone is satisfied), though perhaps if there is a good reason (heavy traffic, better for the kids, etc) an allowance can be made on a case by case basis.

thanks everyone for the suggestions on how to incentivize my nanny. These are good suggestions.

But as this is GQ, I was actually hoping for more insight on the question of relative accuracy. From a couple of you, it sounds like there is no reason to doubt the accuracy of Google, whereas there might be some variability in the odometer-based numbers. Does that sound right?

I always say that my path is arbitrarily close to a path of infinite length. :slight_smile:

It is most likely that the odometer is incorrect. My Subaru Outback has over read by about 5% ever since it was new.

I could find basically nothing about wild inaccuracies from Google but lots of stuff about variances on speedometers due to tire size differences.

For what it is worth, Australian design standards require the speedo to be accurate to +/- 10% and the odometer to be accurate to +/- 4%.

I’m not Telemark, nor did I stay in a Holiday Inn last night, but I believe his (her?) point is that as your nanny is working for you and providing a car and the associated transport services, she should be making a profit. It exactly related, but when I travel for work, my clients don’t just pay my travel expenses as a pass through, my company marks them up to make a profit, standard practice for any place I’ve ever worked.

Mileage reimbursements are for offsetting costs - not for making the employee a profit. If the nanny deserves more money it should be rolled into her actual wages rather than hidden in overgenerous expenses.

I used to drive for a same-day courier service. (San Francisco Bay Area). There were countless instances that a longer route took less time.
Is she on a time constraint and the direct route hits heavy traffic?

We live in a semi-rural area and there is really only one logical best route to most of her destinations. Traffic isn’t really an issue. But I will make it clear that if she does need to divert to a longer route, she should should claim the higher mileage in that case.

As anyone connected with paying out travel expenses will tell you, this is a contentious issue. From the dishonest employee at one extreme who just pads the mileage, to the worker who has the ability to find the most efficient routes at the other, there will always be discrepancies.

In your situation, you are between a rock and a hard place. Google is generally considered pretty accurate (± 5% at least) whereas car odometers, especially 10 year old ones, are not. I don’t know if it’s relevant but the Honda odometer was probably calibrated in miles rather than kilometres. Your dilemma is how much of a stand are you willing to take. The Nanny is effectively asking for a payrise.

Many social workers claim mileages and it may be worth asking to see what they use. You could also check with any friends that might have a similar problem (nannies talk to each other a lot).

Finally, you should consider putting this in any future nanny’s contract.

Just a thought - are the car’s tyres still the original size? Worn tyres turn more times to the Km than new ones…