On the Four Paths

Photo by Jesse Vermeulen, posted at Unsplash.

First Path

In the beginning was the path. It was undifferentiated, shared by people and animals alike, and eventually wheeled vehicles pulled by humans and animals. While dating the First Path is impossible — the very first First Path must have been a path that was reused once, and slightly better than the unimproved space around it — it operated both in early settlements and on routes connecting nearby settlements.

Today’s version of that is the sidewalk or footpath. It is now used for people walking, sometimes for people moving goods, and occasionally for people on scooters and bicycles. It should not be used for storing cars, though it is. New uses will include low speed delivery robots, as shown in the photo from Starship.

When we see a raised crosswalk, we know the First Path is given the pre-eminance its venerable status warrants. When we see shared spaces, we know those harken back to the early undifferentiated path-spaces of earlier centuries. When we see pedestrian-only zones, we see a First Path that has grown up.

Starship Technologies

Second Path

The Second Path diverges from the first path with the emergence of the first street or roads with sidewalks (footpaths).  Spiro Kostof (1992) dates it to about 2000 BCE in Anatolia. And it is clear many Roman and Greek cities separated sidewalks from streets, which the Romans called Semita.

Post-Rome, sidewalks were rare, making appearances in London after the Great Fire, and in Paris after Haussman.

But to be clear, today’s sidewalk is not the second path, it is the first. The second path is the road which is largely free of pedestrians, intended for the movement of vehicles. Originally these were animal powered vehicles, as well as human. Later fuel-powered machines took over the street and roads.

It is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of God.

Third Path

Cyclists Avenue Sydney Cyclists Avenue Sydney (1900)

The Third Path actually emerged well before the Second Path was colonized by motorized vehicles. It is for bicycles, and initially was paved in contrast with the unpaved streets and roads of its time. Given the first Velocipede was only 1817, and the first bike chain (which we associate with modern bicycles) was 1885, these came relatively quickly compared with the First and Second Paths. While ascertaining the first bike lane or separated bike path is tricky (there are many claims, differing in nuance), I have compiled some claimed firsts and earlies here (thanks to people who replied on Twitter):

While bike lanes have now been around as a technology for well more than a century, throughout most of North America and Australia, bike lanes are not provisioned, so bicyclists have the Hobson’s Choice of driving in traffic with much heavier and much faster automobiles and trucks on the Second Path, the roadbed or illegally in many cases on the First Path, the sidewalk.

With the advent of the smart phone, new modes are becoming feasible, most notably dockless shared bikes and scooters.

Regulations in many places limit the use of bikes on footpaths. The reasons for this are clear from the pedestrian’s point of view, bikes are traveling up to 4 times faster than walkers, and collision can create injury. Dockless shared bikes emerged in Australia in 2017, after a few years on the road in China. Their main contribution has however not been transport (they are used about once every 3 days) but instead as a the recipient of complaint about sidewalk clutter (unlike say cars, which are always parked perfectly). As a consequences they have been targets of vandalism. The obvious solution will eventually get adopted, geofenced corrals for parking bikes (shared and private), taking away one parking space per block perhaps.

Given the disparities of speeds on the first (5 km/h) and second paths (30-120 km/h), there is a clear market niche for an infrastructure network  for vehicles faster than foot and slower than cars. Physically, one imagines it generally lying between the existing kerb and removing a lane now devoted to the storage or movement of cars. And for many if not most urban places globally, this has been recognized and networks of third paths have been, or will be, built out.

This Third Path is important not just for bikes, but for electric bikes (which are becoming increasingly feasible with progress in battery technology) and electric scooters.

Fourth Path

A Fourth Path for buses (and other high occupancy vehicles) is also now considered. The first bus lane emerged in Chicago in 1940. The reason for bus lanes again is in part operational differences compared with existing road users. Buses start and stop in traffic much more frequently than cars. But a second reason is in fact the opposite, not because buses would block cars, but because cars would block buses. Buses carry more passengers than cars, and so should move faster, and can do so if they are not stuck in queues behind cars.


The Kerb – Once a nondescript piece of concrete now forms the edge (both physically and metaphorically) of the sharing economy: taxis, Ubers, autonomous mobility services. The Kerbspace differentiates and separates paths, but we now have new questions:

  • Who manages kerbspace? 
  • How is it regulated?
  • Is it even mapped?

Comp(l)ete Streets

The complete streets movement advocates for streets with sidewalks, bike paths, and are otherwise designed to promote safety and efficiency. The figure below is not exactly what they have in mind.

Justicia Urbana by Todorovic (https://www.flickr.com/photos/unhabitat/23003427510)

Fix It First, Expand It Second, Reward It Third: A New Strategy for America’s Highways – Brookings Institution

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

Fix It First, Expand It Second, Reward It Third: A New Strategy for America’s Highways – Brookings Institution by Matthew E. Kahn, Professor of Economics, UCLA Institute of the Environment and Sustainability and
David M. Levinson, RP Braun/CTS Chair in Transportation, University of Minnesota

Abstract: The roads and bridges that make up our nation’s highway infrastructure are in disrepair as a result of insufficient maintenance–a maintenance deficit that increases travel times, damages vehicles, and can lead to accidents that cause injuries or even fatalities. This deficit is in part due to a prioritization of new projects over care for existing infrastructure and contributes to a higher-cost, lower-return system of investment. This paper proposes a reorganization of our national highway infrastructure priorities to “Fix It First, Expand It Second, and Reward It Third.” First, all revenues from the existing federal gasoline tax would be devoted to repair, maintain, rehabilitate, reconstruct, and enhance existing roads and bridges on the National Highway System. Second, funding for states to build new and expand existing roads would come from a newly created Federal Highway Bank, which would require benefit-cost analysis to demonstrate the efficacy of a new build. Third, new and expanded transportation infrastructure that meets or exceeds projected benefits would receive an interest rate subsidy from a Highway Performance Fund to be financed by net revenues from the Federal Highway Bank.

Read the full discussion paper
Read the brief

Fix Old Roads, Instead of Constructing New Ones, Report Urges – NYTimes.com

Our new Brookings report (available tomorrow) makes the Economix blog of the New York Times:
Fix Old Roads, Instead of Constructing New Ones, Report Urges – NYTimes.com

February 24, 2011, 3:50 PM
Fix It and They Will Come
On Friday morning, the Hamilton Project will release a few new proposals for helping fiscally struggling state and local governments keep their roads, bridges and other infrastructure in decent shape. One of the proposals fits a theme I’ve been writing about recently: making government programs less wasteful.
This proposal comes from Matthew Kahn of the University of California, Los Angeles, and David Levinson of the University of Minnesota. The title summarizes it: “Fix It First, Expand It Second, Reward It Third.”
Mr. Kahn and Mr. Levinson call on the federal government to devote its current funding for highways to repair, rather than to the construction of new highways. As they note, the reverse happens all too often:

The way the federal government allocates money for transportation infrastructure investments is one reason why the United States is experiencing a maintenance shortfall and falling returns on new investment. Federal highway infrastructure spending is allocated based on a series of subjective criteria that typically do not require any stringent analysis of expected benefits versus costs. Because there is often public pressure to build new projects using scarce funds, adding capacity often comes at the expense of supporting and enhancing existing infrastructure.

We build roads we don’t need instead of fixing aging roads that we do need. The Kahn-Levinson solution would force state and local governments to spend their federal dollars on repair and to raise money from investors for new construction.
New roads would have to be able to pay for themselves — “through direct user charges and by capturing some of the increase in land values near transportation improvements” — or investors wouldn’t finance them. A newly created Federal Highway Bank would serve as an intermediary between the investors and the state and local governments.
Finally, roads that exceeded expectations — were completed ahead of schedule, for instance, or reduced traffic more than expected — would be eligible for a federal interest-rate subsidy, through the highway bank.
The idea strikes me as promising. The big question, it seems, is how Congress can be persuaded to get out of the business of shiny new roads and concentrate instead on the unglamorous repair work.
The Hamilton Project — which is a branch of the Brookings Institution and tends to be filled with once and future Democratic policy makers — will host an event on Friday to discuss its new proposals.