A council member's exploration of converting Sebastopol's one-way couplet to two-way — and what that could mean for downtown vitality, safety, and the next 30 years.
These are the personal research and policy perspectives of Council Member Phill Carter, shared to support community dialogue. They do not represent official City positions. The underlying engineering study is being conducted by Fehr & Peers under a Caltrans Sustainable Transportation Grant.
The Numbers
The Situation
Sebastopol's one-way couplet was a deliberate engineering choice — and it solved the problem it was designed to solve. The question now is whether that problem is still the right problem to be solving.
The one-way couplet on Main St and Petaluma Ave was engineered to move vehicles through downtown as fast as possible. Peak-hour throughput. Minimum signal delays. That design prioritized the 7-in-10 drivers who were just passing through — not stopping, just getting from one end to the other.
Two-way streets redesign the same pavement for the 1-in-10 who actually want to be downtown — a customer heading to a shop, a family walking to a restaurant. Speed drops, visibility improves, and businesses become accessible from both directions. The data across 20+ cities is consistent: retail sales go up, property values go up, accidents go down.
Historical Context
Sebastopol's one-way street system isn't an accident of geography — it was a deliberate design choice from a specific era of transportation thinking. Understanding that history explains why so many cities are now reversing course.
Following World War II, American cities faced a new problem: postwar automobile ownership was exploding, and existing street grids weren't built for the volume. The dominant planning response — championed by traffic engineers and the emerging Interstate highway system — was to maximize throughput. One-way couplets were a key tool: by separating opposing traffic onto parallel streets, engineers could eliminate left-turn conflicts, synchronize signals for continuous "green waves," and move more cars per hour at higher speeds. Hundreds of American downtowns were reconfigured this way between roughly 1950 and 1975.
The throughput gains were real — but so were the costs that weren't counted. Stores became invisible to half the passing traffic. Pedestrian crossings grew longer and more dangerous as speeds increased. Drivers who missed their destination had to circle an entire block. Property values on converted streets stagnated or fell relative to comparable two-way corridors. By the 1990s, cities that had converted in the '60s were quietly converting back — and finding that the economic gains were substantial and consistent.
How It Actually Works
The most common objection to conversion is "won't traffic get worse?" The consistent finding across converted cities is: no. Here's the logic.
Urban transportation planning calls this functional classification: different road types serve different trip purposes. When a one-way couplet is converted, traffic doesn't disappear — it redistributes. The key finding from Dana Point, Louisville, Savannah, and Vancouver is that the volume feared to "back up" on local roads actually disperses more efficiently across a two-way network. Shorter circling routes mean fewer total vehicle-miles traveled.
Travel data shows roughly 7 vehicles pass through downtown for every 1 trying to reach a downtown destination. The current one-way couplet was designed for those 7. The conversion redesigns the street for the 1 — and routes the 7 more efficiently onto Petaluma Ave, which can serve as a natural bypass corridor. Both user groups win: commuters get a cleaner route, and shoppers get a slower, more accessible Main Street.
Once through-traffic shifts to Petaluma Ave, the west side of Main Street can be reclaimed. Council Member Carter is proposing this space become a social promenade — not just a bike lane, but a linear civic space: wide enough for slow cycling, walking, outdoor dining, and spontaneous gathering. This is the model that transformed streets in European cities and increasingly in California downtowns like Dana Point.
The 31% average speed reduction documented across converted cities isn't just comfort — it's survival. A pedestrian struck at 30 mph has roughly a 20% fatality risk. At 20 mph, it drops to around 5%. And the counterintuitive finding in the Louisville study is that as downtown traffic volumes increased after conversion, accidents decreased — because the streets were designed for interaction, not throughput.
Case Studies
These aren't projections. These are documented outcomes from cities that made this conversion. Small towns highlighted in green — they're the most comparable to Sebastopol's scale.
10–13% annual sales growth. 192,000 sf new retail now supportable. PCH converted to 4 lanes (2+2). Zero net capacity loss. Now a 2028 Olympics sailing destination.
10–20% sales growth. "Coming back to life almost overnight." Significant increase in pedestrian activity and business investment.
39% property value increase on converted Brook St. 2× property tax revenue vs. nearby one-way blocks. Accidents decreased even as traffic volume increased.
Growth after years of decline. "Thriving — experiencing growth." One of the lowest-cost conversions with documented commercial revival.
Business traffic actually picked up after conversion — counter to fears expressed before the project. A case study in pre-project concerns not materializing.
Economic revitalization and additional pedestrian activity documented. Promotes private reinvestment framework — public investment catalyzing private spending.
Regained most of the 2/3 of taxpaying addresses lost during the one-way era. The conversion reversed decades of fiscal damage to the city's tax base.
Dramatic increase in new retail shops, restaurants, and property values. One of the earliest large-city examples to be widely cited in planning literature.
Vacant buildings occupied. "Totally turned the center city around." Often cited as the conversion that shifted professional planning consensus.
2.08% job growth above citywide rate. Part of SDSU context-sensitive framework study examining outcomes across 6 converted cities.
$20.6M annual sales increase projected. 36,000 sf new retail supportable. 16,000 sf new restaurant space. Model used for Sebastopol projections.
Associated with higher retail activity and downtown vitality per Reimagining the Core study. Caltrans grant-funded engineering analysis underway through Fehr & Peers, 2025–2026.
Honest Assessment
This isn't a slam dunk. There are real tradeoffs. Here's a frank accounting of where the conversion is strong, where it's vulnerable, and what has to go right for it to work.
The Plan
A four-part framework for a safer, more productive, more connected downtown Sebastopol — advocated by Council Member Phill Carter as the direction for deeper engineering study by Fehr & Peers.
California Blueprint
Same challenge as Sebastopol: a state-built one-way couplet prioritized regional throughput and fragmented a downtown. Here's what they did — and what happened.
Fiscal Logic
Property value increases aren't just a livability metric — they generate the tax increment that funds the investment. This is the self-reinforcing logic that makes conversion attractive fiscally, not just urbanistically.
Property value increase on converted streets. One-way street blocks declined in value over the same period.
University of Louisville / Property Valuation Administration records
Property tax revenue per block on two-way streets vs. comparable one-way blocks in the same neighborhood.
Center for Sustainable Urban Neighborhoods, Louisville
Enhanced Infrastructure Financing District captures property tax increment from rising values — directly funding the infrastructure that created them. Already under discussion for West County corridor.
California EIFD statute · AB 229 / SB 628
Estimated annual property tax revenue left on the table in Louisville by maintaining multi-lane one-way streets. Sebastopol's scale is smaller — but the ratio holds.
Gilderbloom & Riggs · Planetizen / University of Louisville
Full Record
Green = Small Town · Gold = California · Highlighted = Sebastopol. Sources: SDSU / Riggs & Appleyard, Dana Point EIR, Strong Towns, ResearchGate, City studies.
| City | Type | Est. Cost | Outcomes |
|---|---|---|---|
| Dana Point, CA | California | $21M | 10–13% annual retail sales growth · 192K sf new retail supportable · 2028 Olympics venue · zero capacity loss |
| Vancouver, WA | Small Town | N/A | 10–20% sales growth · "coming back to life almost overnight" · significant private reinvestment |
| Louisville, KY | Small City | $250K | 39% property value increase · 2× property tax/block · traffic accidents ↓ even as volume increased |
| Lubbock, TX | Small Town | $50K | Growth after years of decline · businesses thriving · one of lowest-cost conversions with documented commercial revival |
| Newport, OR | Small Town | $2.7M | Economic revitalization + pedestrian activity · promotes private reinvestment framework |
| Savannah, GA | Historic Core | N/A | Regained 2/3 taxpaying addresses lost in one-way era after 2012 reconversion |
| West Palm Beach, FL | Mid-Size City | N/A | Dramatic ↑ in new retail shops, restaurants, and property values |
| Toledo, OH | Mid-Size City | N/A | Vacant buildings occupied · "totally turned the center city around" |
| Lafayette, IN | Small Town | N/A | Business traffic picked up after conversion — counter to pre-project fears |
| Missoula, MT | Small City | N/A | 10–13% short-term retail benefit expected · part of national pattern analysis |
| Kalamazoo, MI | Mid-Size City | Proposed | $20.6M annual sales increase projected · 36K sf new retail · 16K sf new restaurant space supportable |
| Birmingham, AL | Mid-Size City | N/A | Speed friction ↓ · revived downtown efficiency · simulation-based study |
| Perth, AU | International | N/A | 31% speed reduction · easier navigation for residents and businesses |
| Durham, NC | Mid-Size City | $12M | Planned ↑ for pedestrians, cyclists, and businesses · RAISE grant funded |
| Des Moines, IA | Mid-Size City | N/A | 2.08% job growth above citywide rate · part of SDSU 6-city economic study |
| Sebastopol, CA ★ | Our City | TBD | Associated with higher retail activity + downtown vitality · Caltrans grant funded · Reimagining the Core study 2025–2026 |
Green = Small Town · Gold = California · Highlighted = Sebastopol
Do Your Own Research
The case for two-way conversion is well-documented in transportation literature spanning 30+ years. Here are 20 sources behind this analysis — and search terms to find more.
Add NCHRP, ITE Journal, Transportation Research Record, Strong Towns, NACTO to find peer-reviewed and practitioner sources.
Accessible academic summary of the arguments for and against conversion. Good starting point for understanding the full range of professional opinion.
Peer-reviewed study analyzing traffic operations, safety, and circulation outcomes after Birmingham's downtown couplet conversion.
Rigorous economic analysis by William Riggs advancing a context-sensitive framework. The source for most of the retail sales and property value data cited here.
UChicago research documenting that two-way conversions simultaneously increase traffic, decrease accidents, raise property values, and reduce crime.
Jarrett Walker's influential NACTO paper arguing that one-way systems constrain network efficiency and harm the places they pass through.
Strong Towns makes the financial productivity and community vitality case for conversion in plain language. Widely shared in planning circles.
A skeptical take from a free-market transportation perspective. Worth reading to understand the strongest counterarguments and how they've been addressed in practice.
Detailed before-and-after case study from Louisville examining pedestrian safety, property values, and business activity on a converted corridor.
Dana Point's official planning page. Same California regulatory environment as Sebastopol — Caltrans, CEQA, Coastal Act.
The official Caltrans-funded engineering study currently underway in Sebastopol. Community input is open — add your voice.
Official city page on the grant funding the Reimagining the Core study. Background, timeline, and how to participate.