To answer this question we again turned to the consistently helpful Public Information Officer at the Nevada State Department of Business & Industry, who responded thusly:
"By default, drivers are required to take the most direct route, which is measured by mileage, not time. A passenger may request that the driver take the 'quickest route,' which would leave the route to the discretion of the driver, based on their knowledge of traffic patterns and potential impediments such as construction and traffic lights.
"This issue most commonly arises when a passenger leaves the airport for a destination on the Strip. The 'shortest route' is through town, via Paradise/Swenson. The 'quickest route' often means travelling south on Paradise under the airport tunnel and north on I-15, although depending on traffic conditions, this may not always be the case. I think the most important thing to know is that drivers are required to take the shortest route (by mileage) unless otherwise directed by the passenger. If a passenger wants to get to their destination via a specific route, the driver should comply."
So, there's the official word, and below is the statute governing this:
NRS 706.8846 Prohibited acts concerning destination of passenger. With respect to a passenger’s destination, a driver shall not: 1. Deceive or attempt to deceive any passenger who rides or desires to ride in the driver’s taxicab. 2. Convey or attempt to convey any passenger to a destination other than the one directed by the passenger. 3. Take a longer route to the passenger’s destination than is necessary, unless specifically requested so to do by the passenger. 4. Fail to comply with the reasonable and lawful requests of the passenger as to speed of travel and route to be taken. (Added to NRS by 1969, 1247; A 1977, 750)
In a piece of very timely reportage, however, the Las Vegas Review-Journal earlier this week published the findings of a legislative audit of the state Taxicab Authority, which estimated that 22.5 percent of the 6.6 million rides given by local taxicabs to and from McCarran International Airport in 2012 were deceptively long, overcharging passengers collectively to the tune of $14.8 million.
The good news, however, is that many of the complaints cited in the audit apply to a previous era, with the Taxicab Authority now under a new regime headed by Administrator Charles Harvey, who appears to be serious about clamping down on the notorious practice of long hauling and has introduced stiffer penalties for those drivers caught violating the rules.
As part of the tougher enforcement stance, NTA officials have stopped settling citations for less than the statutory penalties, which range from $100 for the first offense to $350 for the fourth, and have started to recommend that hearing officers suspend taxi licenses for three to 10 days starting with the second offense, with a fifth offense leading to possible license revocation. In a statement last year to the R-J, Harvey announced that, "We know we won't stop long hauling completely. But we want to send a message to create a deterrent."
The Taxicab Authority is also in the process of carrying out its own audit of the state's cab companies, which began in February of this year and should be completed within twelve months, so while a bill that would have required cab companies to establish flat rates between McCarran Airport and various locations on the Strip failed in the Legislature earlier this year, hopefully proactive steps are being taken to curtail the practice of long hauling which, as the Public Information Officer quoted at the top of this answer acknowledged, "may result in tourists having a negative experience," either upon arrival or departure, that in some cases may even deter them from a future visit.
