The media attention devoted to autonomous vehicles implies that they will be the cure for what ails our transportation system. The idyllic vision painted by their advocates is one of recovered personal time and a reduced number of accidents. But there are serpents in this anticipated Eden. Let’s consider them.

An autonomous car can be used as either an upgraded private automobile or as a public taxi. In the former mode, the private autonomous car goes into town, parks for the day, then returns home with its owner. It makes one round-trip per day and requires parking space near the worksite. Alternatively, the private autonomous car takes its owner downtown, drives empty back home or to an outlying parking structure, returns downtown empty at the end of the day, then returns home with its owner. With this usage pattern, the car makes two round-trips per day but requires no worksite parking. The first use pattern continues the parking problems caused by growth. The other pattern produces more traffic on the road and adds to energy use, street noise, and traffic conflicts.

When used as a public taxi, a single autonomous car transports multiple passengers during the day. Because traffic in and out of Boulder are not balanced from hour to hour, autonomous taxis make empty runs out of the city in the morning to pick up additional in-commuters. That means that morning outgoing traffic increases. Similarly, in the evening, incoming traffic grows.

Finally, it is worth noting that there is no guarantee that autonomous vehicles will be electric. Computer-driven gas vehicles are no more sustainable than human-driven gas vehicles.

Autonomous cars might allow drivers to text full-time legally, but it is unlikely that they will reduce the need for road space and parking space any time soon. My car is 20 years old and, if there are other cheap owners like me, in 20 years there will still be many “dumb” cars on the road, interacting (or colliding) with the presumably much-better driven autonomous cars. Pedestrians, bicyclists, and ball-playing school children will continue to share the space—and will die in the process.

We need to expand our vision to consider a wider variety of transit options. In Part 1 of this series, I wrote that the city’s Transportation Master Plan (TMP) must focus as much on the needs and wants of transportation users as it does on the goals of transportation planners. We can do that by augmenting the existing measurable objectives in the TMP with objectives that reflect the needs and wants of individual travelers. That way, we can begin to identify transportation modes that work for both society and the individual.

In pursuit of that goal, I developed a spreadsheet listing the combined criteria from both planners and users along the left side and transportation modes along the top, using the same methodology and cell values that I assigned in Part 1 for each group separately. When I ranked the travel modes according to how well they meet criteria that reflect the values of both transportation planners and transportation users, I obtained the following results: (1) personal rapid transit, (2) walking, (3) self-driving car, (4) gondola, (5 tie) self-driving taxi, (5 tie) bicycling, (7) auto, and (8) bus.

We could add additional travel modes, but the bottom line is that we need a mode that a large percentage of people prefer to use because it works better than cars. Autonomous cars will not be our transportation savior, nor will bicycles, buses, or gondolas. For day and night all-weather usage they are just not going to cut it—although each has certain positives. Autonomous cars save drivers’ time and improve safety, bicycles’ small size makes them adaptable, buses provide service to the elderly and disabled, and gondolas run without traffic interference.

By design, personal rapid transit (PRT) combines many of the positives of the other modes while avoiding the associated negatives. It is that combination of positive attributes that makes PRT the first ranked mode. We can dream about adding autonomous cars to our existing traffic streams, but if Boulder is brave enough and determined enough, we could implement PRT and actually begin to reverse the strain on our roads.

But first we need to be clear about what PRT is. That discussion is the primary subject for Part 3 of this series.

Continue to Part 3