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It is something I have been wondering for a very long time, and I apologise if this question is posted on the wrong site. (Kindly direct me to the correct one if that is the case)

According to the one page I found which explains the fare calculation in the UK in detail, it seems this calculation does not take on board passenger weight: http://www.aquila-electronics.co.uk/how_work.html

How can this be fair, both for the taxi driver as for its passengers?

The amount of fuel consumed is proportional to the weight of the car, its acceleration and speed, and its wind resistance (and the incline when going up a slope)

So one person travelling in a taxi increases the taxi's weight with around 200 lbs (~ 14 stone, 91 kg) for a sturdy rugby player.

However, let's say this rugby player brought 3 team members, bringing the total weight added to the car to 4*200 lbs = 800 lbs (~57 stone, 363 kg)

That is 600 lbs (~ 43 stone, 272 kg) more than the original ride for 1 person.

Quite a significant increase, which has got to affect the fuel consumption of that taxi cab noticeably.

What if the people were even bigger? (I for example am 242 lbs [~17 stone, 110 kg])

Also, going up an incline requires a lot more fuel than driving on a plane…

So in summary:

  • Do taxi meters in this day and age take into account passenger weight ?
  • What about going up slopes?
  • If no, why not, and how would this impact a taxi driver's income?
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  • 41
    Well, a black cab weighs 4354 lb (excluding driver), and most people are not rugby players, so I'm not sure the fuel consumption will in fact be "noticeably" affected. In any case, economics dictates that prices are set not based on costs, but on what people are willing to pay, and I have a strong feeling that people would be much less willing to use taxis if they were priced per-person (or if there was a per-person surcharge), which is not what the taxi drivers/companies want.
    – waiwai933
    Commented Mar 21, 2015 at 10:04
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    Actually. Weight in fact factors very little into the fuel consumption. You should ask the question in SE Physics. But the skinny of it is that the rolling resistance of a car is negligible when compared with the aerodynamic drag of the car (which is constant wrt to the shape of the taxi). So up until the rugby players are so big that they don't actually fit in the taxi, there is no actual noticeable change in fuel consumption.
    – Aron
    Commented Mar 21, 2015 at 19:48
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    @Aron - if you're in gear, the fuel consumption while engine braking is as near zero as makes no difference - 999mpg according to the display in mine. According to this answer on mechanics.se the fuel is in fact completely cut off. As for power brakes, the brake servo has some reserve after the engine cuts out, I haven;t tested the limits on anything recent, nor would I want to.
    – Chris H - UK
    Commented Mar 21, 2015 at 20:01
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    Who told you life was fair?
    – Koray Tugay
    Commented Mar 22, 2015 at 12:30
  • 6
    I've got a private jet charter and although I was the only passenger they billed me the whole amount...Can you believe it?
    – The user with no hat
    Commented Mar 22, 2015 at 23:37

7 Answers 7

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Simply because the fuel cost is only a very small part of the total cab fee and at least until recently, when taxis had mechanically coupled taxameters, it would probably have been much more expensive taking fuel consumption into account than what anyone could have gained by doing so. The major part of the cab fee, perhaps as much as 80-90%, covers the labour cost, which is more or less exactly the same, no matter how many passengers are transported. The rest will cover further expenses like fuel, vehicle maintenance, value loss and out of these, only a few parts are somehow related to passenger weight.

Just as an example: A four mile cab ride in London will cost you roundabout £20. A black cab has an estimated fuel economy of 27 MPG, the diesel is currently about £1.20/l, meaning that the fuel for said trip will cost the driver (or cab company) about £0.85. Depending on passenger weight, traffic and road conditions, the real fuel cost may perhaps be somewhere in the range of £0.60 to £1.20, but compared to the £20 cab fare the difference is very small.

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  • Nice example and nice answer, although London is quite expensive. Here in Plymouth you can go 6 miles (and 20 minutes waiting) for 15 £ (that was a few years ago though). I did not realise though that the difference would be so minor, especially when I hear of people only filling their fuel tanks with 20 litres at a time to safe "fuel"
    – Aethalides
    Commented Mar 21, 2015 at 11:40
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    @Aethalides: those are probably the same people who don't refuel at the closest gas station but at the cheapest, spending considerably more money in gas and lost time than they save.
    – Andreas Bonini
    Commented Mar 21, 2015 at 13:09
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i have never been in a country where the taxi fare changed depending on the number of passengers. If there are seatbelts for 3 passengers, you can take 3 passengers. Some countries charge for bags, others only if there are a lot of bags or the driver handles them.

In general, the weight of the passengers is rather small compared to the weight of the vehicle, and does not make a significant difference to the operating cost.

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    At least in Iran, there are shared Taxis. By default, you can pick a taxi and take a sit. It will wait for more passengers and the cost will be shared. It is not your concern if he be able to find more passengers are not, anyway you will be charged for just one person. However, you have the option to pay for all passengers always if you prefer. It other words, it is like a city bus.
    – Kousha
    Commented Mar 21, 2015 at 22:58
  • Many jurisdictions in the USA have taxi fares that increase as the number of passengers increases.
    – phoog
    Commented Mar 22, 2015 at 3:20
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    Tajikistan, Uzbekistan...have shared taxis. You pay for your seat, wait for taxi to fill up, and away you go. Quite often depending on your haggling skills, you'll pay more or less than your fellow passenger, going to the same place!
    – Mark Mayo
    Commented Mar 23, 2015 at 10:26
  • In my experience in Central Asia you have regular per-car taxis within cities, then shared per-seat taxis for intercity travel, which go from a known semi-official leaving point. Plus per-seat minibuses aka mashrutka within cities, with fixed route numbers.
    – user56reinstatemonica8
    Commented Mar 23, 2015 at 10:55
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Surcharges for Extra Passengers

Here are two counterexamples. In both Italy and France, if I recall correctly, taxis charge extra when the number of passengers require one to seat on the front seat next to the driver. Furthermore, a surcharge can be applied when the customer requires a car with more than 5 seats (including the driver). Note that the concept of a 5-backseats taxi is somewhat unique to the UK, hence in the aforementioned countries when 4 people take a cab one of them usually sits at the front.

Italian Taxis

Indeed, surcharging by person seems to be a relatively common practice across Italian taxi companies. Take for example the pricing list for the Taxis in Padova, Italy:

Supplemento oltre la terza persona trasportata € 1,05/persona

Stating that there is a 1.05€/person surcharge for any number of passangers greater than 3. This applies to both 5-person cars as well as cars with more seats.

The taxi consortia in both Naples and Turin on the other hand, apply a surcharge for any number of passengers greater than 4. The Neapolitan taxi service website says:

Per ogni passeggero oltre il 4° (se l'utente chiede una vettura con un numero di posti superiore a cinque) 1,00€

I.e. when the customer requests a car with more than 5 seats (including the driver), a surcharge of 1.00€ will be applied to each passenger. The Turin taxi service website says:

Supplemento PASSEGGERO oltre il quarto

  • € 3,50 per quinto passeggero
  • € 1,00 per sesto passeggero e oltre

I.e. when the customer requests a car with more than 5 seats (including the driver), a surcharge of 3.50€ will be applied to the fifth passengers, and 1.00€ for each additional passenger.

French Taxis

Similar surcharges apply in France too. Parisian taxis charge 3.00€ for the fourth and any other additional passenger:

Supplement per person over and above 3 passengers € 3.00

The same applies in Nice, where the surcharge is 1.58€:

  • Majoration 4ème personne : 1.58 €.

Turns out these values are usually limited by municipal (administrative) regulations.

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    This is helpful too. You know, I have heard of airlines weighing people to charge more? Or was it that they were planning to do that...
    – Aethalides
    Commented Mar 21, 2015 at 11:43
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    @Aethalides Some airlines talked about it but it was... very unpopular and I don't think any have implemented it.
    – David Richerby
    Commented Mar 21, 2015 at 16:28
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    Is "Some airlines" an alternate spelling for "Ryanair"?
    – Dan Is Fiddling By Firelight
    Commented Mar 21, 2015 at 22:03
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    @DanNeely It is implemented by Samoa Air.
    – gerrit
    Commented Mar 21, 2015 at 23:41
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    @Aethalides It's quite common in the South Pacific, they do it in Tonga too. Small planes, plus "big is beautiful" rugby-loving culture... they also use internal flights for goods, so too many heavy customers could force them to take freight out of the hold. They also need to ensure both sides of the plane are balanced... lots of issues that are unique to air travel.
    – user56reinstatemonica8
    Commented Mar 23, 2015 at 10:49
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That is 600 lbs (~ 43 stone) more than the original ride for 1 person.

Quite a significant increase, which has got to affect the fuel consumption of that taxi cab noticeably.

You are mistaken there. The weight of the car is really a very minor part of the fuel consumption and an even more minor part of the total costs of running a car. So for example the Audi A4 (2002 model) that I sometimes drive (a more or less average size vehicle suitable for 4 persons) as en empty weight of 1665kg, so the 600lbs (less than 300kg) extra would increase the weight by less than 20%. So let's say that my vehicle would consume 8 liters of diesel/100km (which is already a sign of a quite rough style of driving) and let's say weight would be the only parameter which is important, then the fuel consumption would rise by 20% (1.6 liters/100km). So a quick search of diesel prices in the UK suggests a price of around 115.6/liter which would mean an extra of 184p/100km need to be taken into account which is less than 2p/km extra. If we assume a taxi fare of £2.75/km (that's what I found on google without too much verification, but sound realistic) the extra £0.02 is really not worth discussing about whatsoever.

And that's even though I calculated the extra 2p/km considering the weight much more into account than in the reality. The weight of the car only makes a difference while you hit the brake, because that is where you throw away all the kinetic energy that you have. With careful driving and utilisation of remaining energy (e.g. slowly decelerate without hitting the brakes well before reaching that red traffic light in front of you) the total effect can be brought to almost zero. I never noticed a difference in fuel consumption in my cars whether I drove alone or with multiple people.

When I learned that e.g. on the British Virgin Islands taxi fares are per person, which means that a taxi with 3 passengers costs 3 times as much as a taxi with one person, I felt seriously ripped off.

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    +1 This answer is mostly correct, though I would note that it's acceleration where the weight matters directly. The reason braking is inefficient is because it means you've already wasted energy accelerating more than was required. Also, the weight difference will be more noticeable in city driving where you will be stopping and accelerating more frequently, but it will still be so negligible compared to the total cost of operation that charging for it wouldn't be worthwhile.
    – reirab
    Commented Mar 23, 2015 at 18:37
  • @reirab if I'm not mistaken, the kinetic energy of a 1500 kg mass traveling at 36 km/h (10 m/s) is 75 kJ, and the energy density of gasoline appears to be around 34 MJ per liter, so accelerating to that velocity from zero requires at least about 2.2 ml of fuel (plus some more for inefficiency). This figure is directly proportional to the mass, as noted here, so it is indeed on the order of pennies. But "accelerating more than required" doesn't make sense. If the requirement is to move between two points, you have to accelerate and decelerate, which implies braking.
    – phoog
    Commented Apr 5, 2021 at 18:51
  • @phoog Deceleration doesn't necessarily imply braking. While in motion, you will be losing energy to aerodynamic drag, to friction with the surface, and to inherent mechanical inefficiencies constantly anyway. You're going to lose energy to those anyway, so allowing your kinetic energy to be dissipated via that loss that you're going to have anyway (by coasting to a stop over a longer distance instead of braking over a shorter one) is more fuel efficient than braking where you're just intentionally wasting that energy by converting it directly to heat.
    – reirab
    Commented Apr 5, 2021 at 19:20
  • @phoog The extra braking (and, thus, energy loss) required to stop can thus be avoided by simply letting off the gas sooner.
    – reirab
    Commented Apr 5, 2021 at 19:23
  • @reirab but the requirement typically involves a temporal component. Letting off the gas at just the right time to reach a certain lower velocity at a particular point in space and time, for example to make a sharp turn at a safe speed, could well impede traffic. If the road slopes down, braking will be necessary, and even if it doesn't, drag and friction at low velocities result in low deceleration, which means a long time spent at a low speed before finally stopping.
    – phoog
    Commented Apr 5, 2021 at 19:29
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Even in the UK there can be additional cost of additional passengers. This is from guildford council's Taxi Fare Procedure (http://www.guildford.gov.uk/media/14270/Item-4-1---Hackney-Carriage-Fares-App-1---Taxi-Fares-Procedurepdf/pdf/pdf15_1.pdf):

  1. In addition to the charge per mile, we will apply an extra charge for each passenger carried in excess of two. We base this on current practice and local circumstances and this assists the drivers of larger vehicles, which have a lower fuel economy. These vehicles are predominantly wheelchair accessible so we set this extra charge to provide an incentive for such vehicles to remain licensed. We identify this extra charge as Item 9 on the fare calculator.
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  • Note that outside of London, there are very few Taxi in use, it is mostly normal cars with a sign fixed to them that says Taxi.
    – Ian Ringrose
    Commented Oct 4, 2016 at 18:38
  • It varies by local authority, some insist that all "hackney carriages" are wheelchair accessible which pretty much means purpose designed vehicles (though not always traditional black cabs).
    – Peter Green
    Commented Apr 5, 2021 at 10:22
  • @IanRingrose isn't a car with a taxi sign on it a taxi?
    – phoog
    Commented Apr 5, 2021 at 18:53
  • @phoog - if your question gets seen by the driver of a black cab and the driver of a minicab and both decide to reply, you'd best break out the popcorn and settle in to watch the fight.
    – Spratty
    Commented Apr 6, 2021 at 14:32
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In reality, the meter makes it hard. We have the technology, but it most countries Taxis are highly regulated, and you pay for the car by the meter. Published notices display the fare and tariff structure. This is generally law, however you can come to an arrangement with the driver and have the meter off. In Australia, there are small differences between states and even cities. The usual driver scams abound. It is perfectly acceptable in Sydney to share a taxi and each fare pays upon alighting a "weighted proportion". But not for the same destination. As for mass, braking is a "total loss" open circuit drain of energy unless the taxi is a Prius or similar (?). So a lot of stop start is going to add up, but not much. E=(0.5)(m)(v)(v) or a half mass times v squared. Idling and crusing cost the same, and riding lower may increase rolling resistance but reduce drag due to wind resistance.

Too hard, just go with a meter and everybody understands. Otherwise catch a bus.

As an Australian, I still try and grab the front seat in UK taxis, almost crippling myself on a number of occassions.

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    "weighted proportion" will generally be a percentage of the meter to date reading the and last one out pays the balance. It has nothing to do with the actual mass of the pax.
    – mckenzm
    Commented Mar 21, 2015 at 20:10
  • Meters can be programmed to conform with a tariff that charges different fares for different numbers of passengers.
    – phoog
    Commented Mar 22, 2015 at 3:25
  • Yes, but people hate that, and so do the drivers. We have an area here known as the "Gold Coast" and fares for "maxi taxis" are less when they are not at least half full. Most of the time the drivers will rip you off if they can. It's actually cheaper for me to hire a car for two days than pay this fare once.
    – mckenzm
    Commented Mar 22, 2015 at 4:05
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In Israel they have service taxi and special taxi (taxi = monit) ... while the special taxi are just as it's common in Europe (occasionally Mercedes even) - those service taxi work a little different: they just drive around and try to pick up people from bus stops, along the way - while several passengers share the cost of the travel, all having a similar destination. the doors are also to be opened by hand, fold outward, pretty funny. overall, when such a service taxi is full, it's cheaper than the bus ...and more secure.

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    Interesting. So the question now is: how is the fare calculated, and split between passengers?
    – JoErNanO ♦
    Commented Mar 22, 2015 at 13:48
  • the service taxis have no meter - one has to put the kippah on the head ...and start to bargain (low bargaining skill = high price). it's not really split-rate - each passenger pays what they agreed on. even special taxis are merely based on agreement ...best is to try involving several drivers to get a better price. shuttle-service is probably the most similar business model in Europe.
    – user27888
    Commented Mar 24, 2015 at 4:51
  • Good to know. Add this to your answer. ;)
    – JoErNanO ♦
    Commented Mar 24, 2015 at 8:56

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