The Reason Our Streets Switched to Cul-De-Sacs

TL;DR;

• Early U.S. cities followed the 1785 rectangular land-survey grid, which made it easy to plat and sell land and produced walkable street networks.¹
• In the 1920s–40s, Clarence Perry’s “neighborhood unit” concept and Federal Housing Administration (FHA) mortgage rules quietly pushed developers toward school-centered, arterial-bounded neighborhoods instead of open grids.²³
• Transportation engineering standards from the Institute of Transportation Engineers (ITE) then canonized curvilinear streets, T-intersections, and cul-de-sacs as “safer” subdivision design based on an influential but limited crash study.⁴⁵
• Modern research finds that more connected street networks support more walking and cycling and can reduce serious crashes at the network level, even if some individual intersections are busier.⁶⁷⁸
• Today’s best practice is a hybrid: keep quiet local streets if people like them, but reconnect neighborhoods with walking and cycling paths and slower, safer main streets.
• For cyclists who are still forced onto fast arterials by cul-de-sac layouts, high-audibility tools like Loud Bicycle’s car-sounding Loud Mini horn can be a life-saving backup—but they’re no substitute for fixing street design.⁹

“Streets and their sidewalks, the main public places of a city, are its most vital organs.”
— Jane Jacobs, The Death and Life of Great American Cities (1961)

From perfect rectangles to suburban mazes

If you look at a map of almost any older North American city, you’ll see a near-perfect checkerboard of streets. That pattern isn’t an accident; it descends from the Land Ordinance of 1785, which imposed a rectangular survey on much of the U.S., dividing land into townships six miles square and then into 36 one-mile sections.¹ The Public Land Survey System made it cheap and fast to carve up land and sell it, and city grids were the logical extension.¹²

Grids also happened to be pretty good urbanism:

• Many parallel routes mean traffic can disperse instead of funneling to a few big roads.
• Short blocks create lots of corner lots (good for real-estate speculation) and short walking distances.
• Streetcar suburbs in the late 19th and early 20th centuries simply extended the grid along tram lines so people could walk a few blocks to a stop.¹⁰

The City Beautiful channel’s video “The Reason Our Streets Switched to Cul-De-Sacs” tells this story visually and focuses on a simple question: if grids worked so well, how did we end up with a suburban landscape of loops and dead ends?¹¹ The answer turns out to be less about taste and more about institutions: federal housing policy, school-centered planning theory, and engineering manuals.

The neighborhood unit: how schools reshaped streets

Clarence Perry’s big idea

In the 1920s, planner Clarence Perry proposed the “neighborhood unit” as a way to make rapidly industrializing cities more livable.²³ His basic formula, popularized in the 1929 Regional Plan of New York and Its Environs, looked like this:

• Size: A population large enough to support one elementary school, roughly 5,000–9,000 residents on about 160 acres.²³
• Center: An elementary school and playfield at the literal center of the neighborhood, so every child could walk there in about five minutes without crossing a major arterial.²³
• Edges: Busy through-streets around the outside of the neighborhood “cell,” not through it.
• Interior: Local streets only, primarily serving residents and aimed at keeping children away from fast traffic.²³

Perry’s diagrams didn’t require cul-de-sacs, but they did assume a hierarchy of roads: big traffic outside, quiet streets inside.² That was already a departure from the older grid, where almost every street played both local and through roles.

FHA mortgages and the neighborhood unit

The Great Depression turned the neighborhood unit from an interesting idea into federal policy. When private lending collapsed, the newly created Federal Housing Administration (FHA) stepped in to insure mortgages. But it only wanted to back what it considered “sound” investments—so it evaluated not just the house, but the design of the entire subdivision.¹²¹³

Historians have shown that FHA technical bulletins leaned heavily on Perry’s neighborhood-unit model.¹²¹³¹⁴ FHA manuals recommended:

• Arterial roads at neighborhood edges.
• Internal local streets with limited through traffic.
• Sites for schools and parks in the interior of the unit.

These criteria made it much easier to get FHA-backed financing if you followed the neighborhood-unit logic, and much harder if you just platted a simple grid.¹²¹³ Combined with other FHA and local zoning practices—minimum lot sizes, use segregation, and explicit racial discrimination—this helped produce the low-density, socially homogeneous subdivisions that later generations labeled “suburban sprawl.”¹²⁵¹⁴

Crucially, none of this required cul-de-sacs yet. Developers could still use modified grids or short blocks inside each unit. Cul-de-sacs were about to arrive from a different direction: engineering.

Engineers, crash studies, and the rise of the cul-de-sac

The ITE and subdivision street “science”

Transportation engineering split off from general civil engineering in the early 20th century, and in 1930 a group of engineers formed the Institute of Transportation Engineers (ITE). By the 1960s, ITE was publishing widely used “Recommended Practices” for subdivision street design.⁴¹⁵

The 1965 Recommended Guidelines for Subdivision Streets and its successors did a few key things:⁴¹⁵

• Discouraged through traffic in residential areas.
• Favored T-intersections over four-way intersections, based on crash data.
• Encouraged curvilinear, hierarchical networks with local streets feeding collectors, which in turn fed arterials—often using loops and cul-de-sacs.

The turning point was an influential 1950s crash study (often attributed to Marks 1957) that compared early curvilinear neighborhoods to older grids. It found about eight times more crashes on gridded streets and roughly 14 times more crashes at four-way intersections than at T-intersections.⁴⁵ For engineers, the conclusion seemed obvious: fewer intersections, fewer crashes—so design subdivisions to minimize cross-streets.

What that study didn’t handle well was context. Later reviews by the Congress for the New Urbanism and public-health researchers point out that the analysis didn’t adequately control for traffic volume, street width, or crash severity, and it treated local crashes in isolation from the network as a whole.⁴⁵⁶ A quiet cul-de-sac looks very safe if you ignore what happens on the fast arterial you’re forced to use for every trip.

Cul-de-sacs as the “rational” choice

From a developer’s spreadsheet, cul-de-sacs looked great:

• Less total street length than a fine-grained grid, saving on asphalt, curbs, and utilities.⁴⁵
• Streets that carry only local traffic, so they could be narrower and cheaper to build.
• Lots that could be marketed as quiet “refuges” from traffic.

Garden City–inspired projects such as Radburn, New Jersey, had already experimented with superblocks, pedestrian paths, and cul-de-sacs in the 1920s and 1930s.¹¹ But it was only when FHA lending guidelines, Perry’s neighborhood-unit thinking, and ITE’s subdivision standards aligned in the 1950s–70s that cul-de-sacs became the default for new American subdivisions.⁵¹¹

Southworth and Ben-Joseph’s classic paper “Street Standards and the Shaping of Suburbia” documents how these standards, applied across thousands of plats, transformed the urban edge into a sea of disconnected pods.¹¹ City Beautiful’s video distills this process nicely: what looks like a stylistic shift was really an institutional one.¹¹

What we lost when we closed the grid

Longer trips, fewer options

From the point of view of an individual homeowner, a cul-de-sac can feel wonderful: little or no through traffic, kids playing in the street, a sense of seclusion. But at the network level, disconnected cul-de-sacs have several downsides:

• Longer walking distances. Instead of walking a few blocks on a grid, you may have to wind around loops and then along a busy arterial just to reach a store a few hundred meters away “as the crow flies.”⁶⁷
• More driving per person. Studies comparing curvilinear suburban layouts with traditional grids find that residents of connected neighborhoods drive roughly 20–30% fewer miles than people in cul-de-sac suburbs, even when incomes are similar.¹⁶
• Traffic concentrated on a few big roads. Because local streets don’t connect well, almost all car trips end up on arterials, which encourages higher speeds and more severe crashes.⁸¹⁵

Public-health researchers have repeatedly found that higher intersection density and connected local streets are associated with more walking, bicycling, and jogging, even after controlling for demographics.⁶¹³ A review of built-environment factors for cycling similarly concluded that “street connectivity and the presence of cycling paths and facilities are the two most significant built environment factors” influencing cycling rates.⁷

Safety: quieter doesn’t always mean safer

The safety story is more nuanced than “grids good, cul-de-sacs bad.” Some research does find lower crash counts on local streets in cul-de-sac neighborhoods, especially for fender-benders.⁶¹⁷ But when you look at serious injuries and deaths, especially on the arterials that bound cul-de-sac pods, the picture changes:

• A California policy brief notes that grid networks with high intersection density can produce fewer crashes overall than cul-de-sac neighborhoods tied to high-speed arterials, once severity and exposure are considered.⁸
• Dumbaugh’s “Safe Urban Form” argues that wide, fast arterials—and non-orthogonal, “forgiving” designs—are strongly linked to more severe crashes, regardless of whether the surrounding neighborhood has cul-de-sacs.¹⁷
• Intersection studies show that crashes at skewed or “non-orthogonal” intersections, and at non-intersection mid-block segments, are more likely to cause severe injury than those at simple right-angle junctions.¹⁸

The National Civic League summarizes the trade-off bluntly: wide, curvilinear streets and cul-de-sacs may reduce minor collisions, but they worsen overall street safety, especially for children, by encouraging higher speeds and forcing more traffic onto a few roads.¹⁰

Table: Grids vs. cul-de-sac street networks (typical patterns)

These are tendencies, not laws; designers can build safe, connected networks that still feel quiet—and very unsafe grids if they combine high speeds with wide roads. But the pattern from the research is clear: connectivity helps.

How cul-de-sacs shape everyday life

Independence, social ties, and “third places”

The built environment doesn’t just change how we move; it changes how we live. Low-density, disconnected layouts limit access to “third places”²⁰ and have been linked to:

• Reduced independent mobility for children and teens, who cannot safely or conveniently walk or bike to friends’ houses, parks, or after-school activities, especially when all routes require using arterials.³²¹
• Less incidental social contact, as most trips require driving to big roads or parking lots instead of walking past neighbors’ stoops or corner shops.³²²
• Higher risks of sedentary lifestyles, which in turn are associated with obesity and chronic disease.²¹²³

One review of street design and public health notes that the safety of cul-de-sac networks is “inconclusive” once you account for increased danger at major arterials and the way low connectivity suppresses active travel.³ More recent work on perceptions of cul-de-sacs captures a similar ambivalence: residents value low traffic and privacy but also recognize the way disconnected layouts can hinder walking, social cohesion, and access to services.²³

In other words, the cul-de-sac network shifts risk and effort from cars to people on foot and on bikes.

Biking in a cul-de-sac world

For people who bike, cul-de-sacs create a specific kind of danger: you can’t quietly slip through back streets to avoid traffic. To leave the neighborhood, you almost always have to use the same fast, multi-lane arterials as drivers.

That’s one reason some riders add high-audibility safety tools like Loud Bicycle horns, which are designed to sound like a car horn so drivers recognize them instantly. In customer reviews, riders in cities like Boston, New York, and Los Angeles describe the Loud Mini horn as “the biggest safety feature” on frightening routes and credit it with preventing close calls or worse.⁹ On high-speed arterials that exist mostly to serve cul-de-sac subdivisions, having a horn that “speaks the same language” as cars can literally stop a turning driver mid-maneuver.

Still, that’s a coping strategy, not a solution. The evidence is pretty clear: if we want safer, healthier travel for everyone, we have to fix the street network itself, not just arm vulnerable users with louder tools.

Rethinking standards: toward connected, quiet neighborhoods

The good news is that cities and regions are starting to undo some of the damage that 20th-century standards created.

Updating the rulebook

Several state and regional agencies now explicitly promote street network connectivity as a design goal:

• A Washington State guide on street connectivity emphasizes that adding local connections reduces traffic and delays on arterials and “enhances bicycle and pedestrian travel when the number of street connections or local intersections is increased.”²⁴
• A 2025 California Air Resources Board policy brief concludes that higher intersection densities typically reduce vehicle-miles traveled, emissions, and, in many cases, serious crashes compared to disconnected networks.⁸
• The Utah Street Connectivity Guide and similar documents encourage minimum intersection densities, block-length caps, and connectivity indexes for new developments, while still allowing short local streets and small cul-de-sacs.²⁵

These policies don’t ban cul-de-sacs outright; instead, they aim to ensure that the neighborhood as a whole remains permeable, especially for walking and cycling.

The hybrid future: cul-de-sacs for cars, paths for people

City Beautiful’s video ends on a hopeful note: the next generation of suburban street design might be a hybrid where cars still see cul-de-sacs, but people don’t.¹¹ In practice, that can mean:

• Short pedestrian and bike paths at the ends of cul-de-sacs that connect to parks, schools, or parallel streets.
• Local street grids that are traffic-calmed (e.g., with modal filters) rather than dead-ended, so through-driving is discouraged but walking and cycling remain easy.
• “Complete Streets” arterials that are narrower, slower, and designed to be safely crossed on foot or by bike, rather than functioning as semi-freeways.¹⁵²⁶

Some European suburbs already implement this idea: cars must take relatively indirect routes on a hierarchical network, but people on bikes and on foot can take short, direct paths between units. The result looks like cul-de-sac land on a road map but behaves more like a permeable grid in daily life.²⁷¹⁵

If we pair that kind of network with high-quality sidewalks, protected bike lanes, and safe crossings—and, yes, with good safety equipment like bright lights and audible horns where needed—we can keep the genuine benefits people associate with cul-de-sacs (quiet, low traffic) without sacrificing safety, health, and access.

FAQ

Q1. Are cul-de-sacs always bad for safety?
A. Not necessarily: individual cul-de-sac streets are usually calm, but when a whole area is built this way, crashes and danger tend to shift to the bounding arterials, where speeds and injury severity are higher.⁸¹⁰¹⁷

Q2. Why did engineers trust that old crash study so much?
A. It offered clear, quantitative support for a simple idea—fewer intersections, fewer crashes—at a time when automobile traffic was exploding, and it fit neatly into emerging engineering manuals from ITE.⁴⁵

Q3. Can we retrofit existing cul-de-sac suburbs?
A. Yes, though it takes political will and money: cities can add pedestrian and cycling cut-throughs, calm arterials, and, where possible, punch through street connections as lots redevelop, improving access without bulldozing whole neighborhoods.⁸²⁴[^27]

Q4. Do connected grids automatically make people drive less?
A. Not by themselves, but higher connectivity consistently supports more walking, biking, and transit use, especially when combined with nearby destinations and safe facilities.⁶⁷¹³²¹

Q5. Where do bike horns like the Loud Mini fit into all this?
A. They’re a useful safety backup for cyclists stuck on fast roads created by cul-de-sac planning, giving them a way to cut through driver inattention, but they don’t fix the underlying problem of disconnected, car-dependent street networks.⁹

References