Were metered taxis busy roaming Imperial Rome?

Question

While in Rome, I heard a claim that Ancient Romans had invented the taxi meter.

"Ancient" here means the common usage of "a long time ago" instead of a specific historical period such as the Early Republic.

Claim: Ancient Roman taxis had meters. A taxi in Ancient Rome had a crude mechanical odometer of some sort that was attached to a wheel that, according to distance, used gears or belts or wheels to deposit stones from a container of some sort into a cup. When the taxi arrived at the destination, the customer would pay accordingly. Differing versions of the claim exist at this point. The one I heard used a balance scale to compare the accumulated stones to silver coins paid by the customer, which could mitigate the problem of intentionally nibbled silver coins in circulation. Other versions simply count the number of stones to set the fare.

Finding a detailed, duplicate claim on the web has been difficult, which makes me suspicious of it as some sort of oral myth spread among tourists and guides.

A taxi meter manufacturer in India credits Ancient Rome

Taximeters have evolved over the years from those in ancient Rome functioning from Axle-release-balls mechanism to the present day Global Positioning System - equipped Data Terminals and the works.

The November 1960 issue of Popular Science states:

In ancient Rome, some hired vehicles had a primitive taxi meter. A compartmented wheel driven by a road wheel dropped pebbles from a hopper into a box. Counter at the end of the ride, these set the fare.

However, wikipedia:Taxicab makes no mention of it in the History section, claiming:

The first documented service was started by Nicolas Sauvage in Paris in 1640.2

But, wikipedia:Odometer mentions ancient versions:

[from Wikipedia Odometer: History] Classical Era

Possibly the first evidence for the use of an odometer can be found in the works of Pliny (NH 6. 61-62) and Strabo (11.8.9). Both authors list the distances of routes traveled by Alexander the Great (r. 336-323 BC) as measured by his bematists Diognetus and Baeton. However, the high precision of the bematists's measurements rather indicates the use of a mechanical device. For example, the section between the cities Hecatompylos and Alexandria Areion, which later became a part of the silk road, was given by Alexander's bematists as 529 English miles long, that is with a deviation of 0.4% from the actual distance (531 English miles). From the nine surviving bematists' measurements in Pliny's Naturalis Historia eight show a deviation of less than 5% from the actual distance, three of them being within 1%. Since these minor discrepancies can be adequately explained by slight changes in the tracks of roads during the last 2300 years, the overall accuracy of the measurements implies that the bematists already must have used a sophisticated device for measuring distances, although there is no direct mentioning of such a device.

An odometer for measuring distance was first described by Vitruvius around 27 and 23 BC, although the actual inventor may have been Archimedes of Syracuse (c. 287 BC – c. 212 BC) during the First Punic War. Hero of Alexandria (10 AD - 70 AD) describes a similar device in chapter 34 of his Dioptra. The machine was also used in the time of Roman Emperor Commodus (c. 192 AD), although after this point in time there seems to be a gap between its use in Roman times and that of the 15th century in Western Europe.3 Some researchers have speculated that the device might have included technology similar to that of the Greek Antikythera mechanism.[4]

The odometer of Vitruvius was based on chariot wheels of 4 feet (1.2 m) diameter turning 400 times in one Roman mile (about 1400 m). For each revolution a pin on the axle engaged a 400 tooth cogwheel thus turning it one complete revolution per mile. This engaged another gear with holes along the circumference, where pebbles (calculus) were located, that were to drop one by one into a box. The distance traveled would thus be given simply by counting the number of pebbles.[4] Whether this instrument was ever built at the time is disputed. Leonardo da Vinci later tried to build it himself according to the description, but failed. However, in 1981 engineer Andre Sleewyck built his own replica, replacing the square-toothed gear designs of da Vinci with the triangular, pointed teeth found in the Antikythera mechanism. With this modification, the Vitruvius odometer functioned perfectly.[4]

But... no mention of taxi meter applications.

It is well known that Ancient Rome had a number of remarkable achievements, including concrete aqueducts and roads and a population over 1 million.

Did Ancient Rome have taxicabs with metered payment, or is that a myth for modern tourists?

Answer 1

Yes.

In addition to the 1960 Popular Science article you mention there was a 1923 Popular Science article: TAXI METERS USED IN ROME:

Before the time of Julius Caesar, ancient Romans were called upon to travel in chariots for which they paid by a crude method of counting distances, according to a recently discovered records. The "taxicab" had a device like an hourglass, by which a pebble was dropped into a bowl for about every 5,000 feet traveled. At the end of the journey, the driver would count the stones, thus arriving at the fare to be paid by the passenger.

From the 1875 A Dictionary of Greek and Roman Antiquities

CI′SIUM a gig, i.e. a light open carriage with two wheels, adapted to carry two persons rapidly from place to place. Its form is sculptured on the monumental column at Igel, near Trevesº (see woodcut). It had a box or case, probably under the seat (Festus, s.v. Ploxinum). The cisia were quickly drawn by mules (cisi volantis, Virg. Catal. VIII.3; Cic. Phil. II.31). Cicero mentions the case of a messenger who travled 56 miles in 10 hours in such vehicles, which were kept for hire at the stations along the great roads; a proof that the ancients considered six Roman miles per hour as an extraordinary speed • (Pro Roscio Amer. 8). The conductors of these hired gigs were called cisiarii, and were subject to penalties for careless or dangerous driving (Dig. 19 tit. 2 s.13).

According to Bill Thayer's University of Chicago hosted website on ancient Rome:

You might say that the cisium was the nearest Roman equivalent to our taxi. If so, by good fortune, we still have the remains of one of the world's grandest taxi stands: at Ostia, the port of Rome, where just inside the city gate coming from Rome, the guild of cisiarii had their own lavishly decorated baths, usually known by their Italian name, Terme dei Cisiari.

The whole set-up is quite logical: there must have been constant traffic between Rome and its port, with busy merchants in a hurry to get themselves or papers or money from one to the other, putting the drivers under a good deal of pressure; so right on the Via Ostiensis near the Porta Romana, a place to clean up and decant.

See also:

Vitruvius' Odometer Scientific American vol. 254.

and

THE ODOMETER BY VITRUVIUS AND HERON

or this source:

An odometer is a device used for indicating distance travelled by a vehicle. Vitruvius around 27 and 23 BC describes such a device and Hero also describes an odometer in chapter 34 of his Dioptra. Chariots with wheels of 4 feet diameter turns exactly 400 times in one Roman mile. For each revolution, a pin on the axle engage a 400 tooth cogwheel, thus making one complete revolution per mile. This engages another gear with holes along the circumference, where pebbles (calculus) are located, that drop one by one into a box. The number of miles travelled is given simply by counting the number of pebbles

Image from The Legacy of Rome, Clarendon Press 1923