23 April 2023
A few weeks ago, my family and I drove to California to visit some family. This gave me an opportunity to experience and reflect upon one of the recurring features of California highway driving: high-occupancy vehicle (HOV) lanes, or, as they’re more commonly known, carpool lanes.
Unlike a lot of Southern Nevada drivers — including, apparently, Republican Lt. Gov. Stavros Anthony — I don’t spend my weekday commutes seething at an empty lane while I inch my way through an interstate-grade parking lot each morning. Living in Northern Nevada, I can approach the subject of carpool lanes somewhat more philosophically. The Nevada Department of Transportation isn’t likely to install a carpool lane in Reno anytime soon, and, due to the mountains immediately west of us, there aren’t any lanes to sacrifice for one on the California side of any of our outbound highways.
While driving through certain stretches of California, I had to admit to myself that the intricacies of the Golden State’s Express Lanes and their corresponding FasTrak toll road system required a bit more study than one could realistically expect to receive while driving past them at freeway speeds. On the one hand, they were theoretically free to use for cars containing three or more persons — a threshold which, owing to being full of a family driving on vacation, my car reached with ease. On the other hand, lane access was still restricted since we lacked a special transponder.
Many stretches of California, however, including the freeways near Sacramento, have more traditional toll-free carpool lanes — the same type of carpool lanes installed in Las Vegas, in fact, albeit without the Active Traffic Management features installed on Southern Nevada’s freeways through the course of Project Neon. It occurred to me while I hustled my family through some of these more traditional carpool lanes — and past several solo drivers in unrestricted lanes — that carpool lanes didn’t seem so bad for tourists, especially if they were visiting as a group or as a family.
This experience left me with a question: Why was Lt. Gov. Anthony so hellbent on getting rid of carpool lanes?
Why did he, as an NDOT board member, push so hard to get the agency to reduce the restrictions on those lanes? Republicans are notionally pro-family. What’s more pro-family than, “Here, working family driving your future Republicans to school — have a dedicated lane for your travels”? Besides, isn’t getting masses of tourists in and out of Clark County in a hurry the entire point of Southern Nevada’s economy?
The answer, it turns out, is our lieutenant governor is actually right about carpool lanes: They don’t work.
To see why, we first need to understand the problem high-occupancy lanes more generally are designed to solve. Thankfully, we don’t need civil engineering degrees to get to the bottom of this — grade school arithmetic will do the job quite nicely.
The fundamental problem is real estate. People driving alone in cars at freeway speeds need a lot of it.
According to the National Association of City Transportation Officials, a car traveling at 65 miles per hour — Nevada’s most common urban freeway speed limit — requires approximately 345 feet to come to a complete stop. Per Edmunds, meanwhile, the most common vehicles sold in North America last year were the Chevrolet Silverado and the Ford F-Series, two pick-up truck models which are both roughly 12 feet long.
If you add the two numbers together, you have the length of road required for the most commonly sold vehicles to safely travel at freeway speeds: 357 feet. Anything less than that and someone traveling at freeway speeds might not be able to safely stop before they rear-end the car in front of them.
According to the U.S. Department of Transportation Federal Highway Administration, meanwhile, lanes on interstate highways are typically 12 feet wide. Multiply lane width by the required length specified previously and you have the total surface area required for each car traveling at freeway speeds: 4,284 square feet.
That’s a lot of real estate for one car, but, if you’re driving on Interstate 80 in rural Nevada, drivers can take all the space they need — there’s more than enough for everyone. In an urban environment, however, giving every commuter 4,284 square feet of real estate to travel to work in gets unwieldy fast.
For example, according to the Current Employment Statistics maintained by the Department of Education, Training and Rehabilitation, 1,118,000 people were employed in the Las Vegas-Paradise Metropolitan Statistical Area — that’s the U.S. Census’ bureaucratically fussy way of saying “Clark County.” If we multiply the number of workers (1,118,000) by the amount of space their cars need to travel safely at freeway speed (4,284 square feet), we would need to build billions of square feet of highway — 4,789,512,000 square feet, or 171.8 square miles — to safely accommodate every commuter who wants to drive 65 miles per hour on their way to work.
To put that number into perspective, the City of Las Vegas is just under 142 square miles.
In short, it would take enough pavement to cover the entirety of Las Vegas, plus a healthy chunk of neighboring jurisdictions, for every commuter in Clark County to be guaranteed the ability to commute at freeway speeds at the same time. This is, of course, absolutely impossible to do, not that anyone would actually want to.
Now, before a committee of angry civil engineers floods my inbox with actual professional traffic studies (go ahead and send them — they’re enjoyable reading), the above is meant to be more of an intuition pump than a formal estimation of the amount of pavement we might need to pour to solve freeway traffic once and for all. There are some erroneous assumptions baked into that estimate that we should break down before we put a capital improvement plan together.
For starters, not all commuters leave for work at the same time, especially in a 24-hour workplace like Las Vegas. Commuters also aren’t going to have to come to a complete stop on the freeway on all of their commutes, so we can reduce the amount of square footage further by cutting into that safety cushion. Commuters also generally don’t live next to freeway onramps, either, so portions of their commutes will be conducted at considerably slower speeds, further reducing the amount of real estate required to safely accommodate them.
On the other hand, commuters also aren’t evenly distributed. If even a sizable proportion of Clark County’s workers need to commute to the same location — say, the Strip — it won’t matter how much pavement was laid down before they got to work since they’d have to come to a stop and wait for their turn to enter their preferred parking garages. Also, speaking of the Strip, the rough estimate provided above didn’t include a single visitor driving in from California nor a single retiree leaving Anthem for a pleasure cruise.
Either way, speeding cars require a lot of real estate. That’s a problem since, at some point, people prefer to build houses, shops and workplaces instead of additional freeways — especially since freeways, unlike residents and businesses, don’t pay taxes.
Consequently, the goal for traffic engineers and city planners over the past five decades or so has been to convince some people — not everyone, but some people — to at least think about leaving their car at home. Doing so, however, requires traffic engineers to provide — or at least accommodate — alternatives.
The most obvious alternative, of course, is also the cheapest: walking.
Walking has much to recommend it: It’s good exercise, people can also walk on just about anything as long as it’s level, and a pedestrian doesn’t require 4,284 square feet to travel safely. In fact, you could lop three of any four of those numbers off and come fairly close to the amount of space people need to comfortably walk next to each other.
Walking is also an absolutely miserable way to have to travel during the summer or winter months. It’s also slow enough to be limiting — even in a dense, walkable city, most people will want to be able to routinely travel more than a few miles from their home, especially if the most profitable work they’re qualified for isn’t located directly next to their front door. It’s also not something everyone can easily and reliably do — injuries and age can both decrease mobility.
Everything said about walking applies just as much to bicycling, with a few minor exceptions — speed and range are increased, but bicycles aren’t free. Bicyclists also tend to be a bit pickier about terrain than pedestrians — it’s more challenging to bike on grass or sand than it is to walk on it.
Human-powered transportation, then, can’t be the sole alternative to car travel, especially since car-centered infrastructure tends to come at the expense of human-centered infrastructure. Nobody likes walking through, much less by, parking lots, especially when it’s 105 in the shade and the black asphalt soaks up summer heat like a sponge.
The next alternative, then, is mass transit. Mass transit generally comes in two forms: trains or buses. Generally speaking, rail-based mass transit tends to be capital-intensive, meaning they’re expensive to build (especially in this country), but can achieve higher capacities and correspondingly lower costs per passenger-mile than buses.
Bus lines, conversely, are comparatively cheap to roll out, especially since they can reuse existing car-centered infrastructure, but are operationally expensive — since buses usually have lower passenger-carrying capacities than trains, more bus drivers must be hired and paid to get passengers to their destinations. Additionally, since buses frequently use the same infrastructure we use for our cars, they frequently get stuck in the same traffic jams we do — when they’re not causing traffic jams by stopping at bus stops.
Regardless of the mode of mass transit chosen, however, they’re all noticeably more efficient than what most of us use to get around:
ModeVehicle Dimensions (length x width m)Transit Unit Capacity (seat + standing spaces)Minimum headway (s)Maximum Frequency (transit units per hour)Line/Lane CapacityPersonal vehicle5.90 2.5013-21200-18001,200-1,800Personal vehicle (plus passenger)5.90 2.5023-21200-18002,400-3,600Standard bus12.00 2.507570-5051-723,800-5,400Articulated bus18.00 2.512080-6045-605,400-7,200High-capacity bus (Bus Rapid Transit)22.00 2.5016030-12120-3009,000-30,000Light Rail Transit (partially separated Right-of-Way)24.00 2.653 170 = 510 or 2 280 = 560150-7524-4812,200-26,900Metro Rail Transit21.00 3.1510 240 = 2,400150-12024-3067,200-72,000
Personal vehicle dimensions based on vehicle dimensions of the most commonly sold personal vehicle sold in the United States in 2022. Minimum headway for personal vehicles based on “three-second rule” or “two-second rule” between followed vehicles. Mass transit figures copied from Zhang, M. (2009), Bus Versus Rail, doi:10.3141/2110-11.
Note that, for a single freeway lane to come even halfway close to matching the carrying capacity of a single standard bus line, it takes a combination of increasingly aggressive tailgating and at least one mandatory passenger in every single vehicle using that lane — assuming we can safely count the driver and the passenger as people in transit. We don’t count the bus driver or train conductor when calculating transit capacity, after all.
More on that assumption in a bit.
Also note, however, how poorly standard buses and light rail perform compared to other, similar modes of transit. Part of the issue with both of those modes is they have to share space with cars — which means they get stuck in the same traffic the cars they’re supposed to replace get stuck in. Since they also have to frequently stop to let passengers embark and disembark, any mass transit option that shares space with cars is guaranteed to be slower than the cars they’re surrounded by, which are usually just driven from point A to point B — which means they’ll always be the choices of last resort, only selected by those who don’t have or can’t afford a car.
To make mass transit competitive against cars — to make it better — it needs its own dedicated lanes. That’s why the first permanent high-occupancy vehicle lanes — again, not carpool lanes, but dedicated bus lanes — were first constructed more than 50 years ago. The Shirley Highway corridor of Northern Virginia, which runs by the Pentagon, had a serious traffic congestion issue from the moment it was constructed immediately following World War II. To help address that, a pair of permanent reversible lanes dedicated solely to bus traffic were constructed from 1969 to 1971.
Carpool lanes, by contrast, were first conceived to address a suite of different problems. The Arab Oil Embargo in 1973 led to a petroleum shortage that needed to be addressed immediately — not after a series of public meetings addressing siting of bus routes or rail transit lines.
At the same time, urban air quality throughout the country — exacerbated by the widespread use of leaded gas — was generally abysmal. To address both issues in a more timely fashion than would otherwise be possible, carpool lanes — lanes dedicated to passenger vehicles carrying a minimum of either two or three passengers — were developed to quickly repurpose existing infrastructure in ways that might reduce gasoline consumption and improve air quality.
The Shirley Highway HOV lanes were among the first to be converted to allow carpools in 1973. California would subsequently plan a network of carpool lanes throughout the state — though, in a demonstration that some problems, like the speed of our western neighbor’s government, are older than we might think, they weren’t successfully deployed for another decade.
Twenty years after they were first conceived, it was already clear carpool lanes didn’t really work. As one report put it: “A car with two occupants is a low occupancy vehicle, not high occupancy: a date is not a carpool.”
Nowadays, we can further add that a rideshare isn’t a carpool, either. The only meaningful difference between a taxi, Uber or Lyft with one passenger and a passenger driving their own car is that someone is getting paid at the end of the trip. From a practical perspective, the same number of people are being transported from point A to point B using the same amount of real estate needed to transport someone who’s driving alone — the only difference is the taxi or rideshare can legally use the carpool lane.
Part of the issue, as Lt. Gov. Anthony has pointed out, is there’s no economical way to apply universal, immediate enforcement. Every officer monitoring carpool lanes for compliance is an officer not performing as a first responder or not reacting to reckless driving elsewhere in the highway system.
The bigger issue, however, is carpool lanes are simply incapable, under even the most generous of assumptions, of meaningfully improving traffic flow. At best, they provide express service for taxis and families. At worst, they consume political and financial capital that would be better spent on services that actually have a fighting mathematical chance of reducing the amount of land we need to dedicate toward roads and freeways.
If we want to actually get cars off the road — or, more accurately, want to devote portions of our desert landscape to something other than streets for cars — we need to actually be willing to move people en masse at scale. Doing so, however, requires actual high-occupancy lanes — meaning, dedicated rights of way for buses and trains.
David Colborne ran for office twice. He is now an IT manager, the father of two sons, and a weekly opinion columnist for The Nevada Independent. You can follow him on Mastodon @[email protected], on Twitter @DavidColborne, or email him at [email protected].
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