Reconstructing the Street? Move the Curb!

(Source: Strong Towns/Chuck Marohn.)

Like diet and exercise leading to healthier living, transformation into a Strong Town is the result of a long-term commitment to bottom-up action. There is no sweeping change or large transformation that can give a city lasting prosperity, but there is an endless list of small things we can do to continually make things better.

One such opportunity presents itself when doing a street reconstruction project. Where a routine maintenance project typically involves some type of repair to the road surface, a full reconstruction project is more involved. If your city is replacing the underground utilities, that generally means the street is being reconstructed and not merely maintained.

If the reconstruction project involves replacing the curb, don’t miss the once-in-a-lifetime opportunity to do something transformative.

You can reduce project costs, reduce long-term maintenance costs, improve safety, reduce environmental impacts, and make the surrounding neighborhood a more pleasant and financially productive place by doing one simple thing: move the curb.

I could have said "narrow the street," but I’m intentionally focusing on the location of the curb here. That is the key thing; get that curb moved! Design engineers have all kinds of ways to claim they have narrowed the street on paper that don’t translate into the real world. Move the curbs and everything changes.

(Source: Strong Towns/Chuck Marohn.)

Real Financial Impact

This summer, my city is working on a street reconstruction project near my home. My commute has been torn up for most of the summer, forcing me to walk through loose dirt and construction debris or take a more circuitous route. I’ve not minded at all. You see, my city moved the curb and I’m ecstatic about it.

Many decades ago, my poor and generally cash-strapped city took a quaint and walkable neighborhood and decided it was going to spend absurd amounts of money widening the streets. In a very practical sense, a wider street substitutes asphalt pavement for turf. The wider the street is, the more pavement and the less turf there is.

Let me state the obvious: pavement is vastly more expensive than turf. Oh so much more expensive. By shifting to pavement from turf, the city is choosing to spend a lot more money upfront.

How much more? The bid tabulation for the current project gives a rough idea.

With an eight-inch-deep section, a shift from turf to pavement increases the cost by 350%. On the pavement side, there is compacted aggregate and bituminous pavement at a cost of $2.09 per square foot. On the turf side, there is fill (common borrow) and topsoil at just $0.60 per square foot. These prices will vary for different locations and different projects, but the ratio of 3.5x seems like a solid benchmark.

I’m not sure exactly how much the city moved the curb, but I estimate about eight feet on each side. If so, they cut well over $150,000 off the cost of the project. Here’s a link to the bid tabulation and a spreadsheet that shows how I came up with these results.

Those are the initial construction costs, but the ongoing maintenance costs add up, as well. Every routine maintenance project over the years had to crack seal, seal coat, and overlay that much more pavement. Every time it snowed, the plows needed to clear that much more snow at a shockingly high cost. When it rains, we have to convey that much more water through systems that must be sized to handle all that unnecessary pavement.

An extra foot of street pavement is the extravagant luxury good we not only don’t appreciate, but also never really wanted.

If you’re reconstructing the street, reduce the street width by moving the curb in. As far as possible. Every foot saves you money today and every year you maintain that street. Fight for less.

My city moved the curb. That’s great leadership.

(Source: Strong Towns/Chuck Marohn.)

Beyond the Financial

Municipalities across North America are financially insolvent. Unnecessarily wide streets are a grotesque extravagance that displays a complete lack of fiscal awareness, not to mention basic prudence. We must move the curbs in for financial reasons, but the irony is that we sacrifice nothing—and gain so much—in the process.

Narrower streets slow traffic. While this isn’t a strategy for high-speed roadways where the extra width is needed for safety, we titled this article "reconstructing the street" for a reason. On local streets, the priority must shift from automobile throughput to human safety and wealth creation. If we want safe streets, we have to design them to be safe, and that means bringing the curbs in to tighten up the space.

Download this handy infographic here!

When it comes to wealth creation, narrower streets also outperform the over-engineered variety. Beyond the obvious observation that nearly all of us prefer to live on quiet, neighborhood streets with slow traffic (and greater preference correlates to greater market price), narrow streets where people feel more comfortable walking and biking provide more investment opportunity.

Your city might not be ready to bring back corner stores and other bottom-up neighborhood businesses, but they will probably never be if you don’t move the curb. Narrower streets create the virtuous feedback loop of more neighborhood housing demand driving more neighborhood business demand driving more neighborhood housing demand.

Then there are street trees. There is no higher-returning investment that a city can make than to plant street trees. Every dollar spent returns many multiples. Move the curbs and not only do you have the room to plant trees, but those trees also have a greater chance of survival.

And when those trees mature, they do so many things. They dramatically lower temperatures in the heat and reduce wind in the cold. They soak up water in the wet and transpire water in the dry. They make walking more pleasurable and, when planted between the sidewalk and the curb, incrementally safer.

And anything that gets people out walking improves public health, allows families to become less auto dependent, keeps more of a community’s wealth local, and so much more.

All this is possible just by moving the curb. Don’t throw away your shot.

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Charles Marohn—known as "Chuck" to friends and colleagues—is the founder and president of Strong Towns. He is a land use planner and civil engineer with decades of experience. He holds a bachelor’s degree in civil engineering and a Master of Urban and Regional Planning, both from the University of Minnesota.

Marohn is the author of Strong Towns: A Bottom-Up Revolution to Rebuild American Prosperity (Wiley, 2019) and Confessions of a Recovering Engineer: Transportation for a Strong Town (Wiley 2021). He hosts the Strong Towns Podcast and is a primary writer for Strong Towns’ web content. He has presented Strong Towns concepts in hundreds of cities and towns across North America.

Charles Marohn·September 11, 2023

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  • Kind of. The vast majority of street projects I've been involved with as an engineer have NOT involved scraping everything back to bare dirt and starting over. In 27 years (admittedly a consultant, not a public works employee), I've never seen a road job that involved total curb replacement unless it was a WIDENING job. Most of the time, they walk the job and spray paint the bad sections of curb, cut that out and splice in new. At common pay rates of $27/foot, total curb replacement gets more expensive rather fast. Total replacement of the roadway is just as rare. Mostly what happens is that a 1.5-2" layer is milled off the top, then what's left is inspected and bad sections are (again) spray painted for sawcut and removal down to the subgrade. If the subgrade is poor, that might be undercut and replaced as well. Then after all the patch work is done, a surface course is paved over the top of it all making it look all brand new again. Perhaps it differs from state to state, but that's my experience.
    If the town really is scraping things back to the dirt and starting over, why settle for merely moved curbs? Why not get a narrower pavement AND eliminate the curbs in residential areas? Grassy swale drainage does a far superior job of cleaning up stormwater, slightly slows down runoff such that old and possibly undersized storm sewers work better, it makes narrowing the roadway easy and the resulting parkway is much better suited for trees growth. I've never understood the fetish for curbs in residential neighborhoods. In dense urban areas I see the benefits, but certainly not in single family house neighborhoods where the sidewalk isn't adjacent to the curb anyways.

      • Adding on to this, do you have any thoughts on using brick pavers on smaller streets during a complete renovation? I've heard that while very expensive in the short term, they last far longer than asphalt, to the point of being noticeably cheaper long term. But I wasn't sure of the hype.

        I know they also make for excellent traffic calming, too. The Netherlands seems to brick pave pretty much all their quite neighborhood roads, even out in the suburbs, so I'm wondering if it indeed pays off.

          • Every traffic engineer I know hates pavers. Because after years two-three-four of freeze-thaw cycles, they get lumpy, and now you have a trip-and-fall hazard.
            You can get the same effect by applying an embossed pattern to your paving material.
            I speculate that the Netherlands are more willing to spend money on frequent maintenance, plus they have fewer freeze-thaw cycles.

              • Most of the time that's an indicator of inadequate subgrade drainage. If they'd provided a somewhat thicker layer of washed angular crushed stone (CA-7 in Illinois-spec speak) and an under-drainage system, you don't get nearly as much heaving. The pavers become just a surface over an aggregate road.
                I'm being a geek and hogging the responses today. Sorry, y'all!

                  • And a brick pavement filled with lumpies and bumpies is an invitation for anyone who gets injured tripping over a brick or twisting an ankle on a gap to sue the engineer, personally.

                      • Not to call you out on this one, Edward, but I hear this a lot from engineers and it doesn't play with me. The same exact people don't fret over being sued about cracked and broken sidewalks, just smooth pavement surfaces.

                        That might not be you, but it is one of the common things people in the profession repeat and it's just not true.

                          • I've been in the profession for 27 years now and have seen some pretty crazy lawsuits in that time. Brick paver trip hazards are not among them. More ADA nitpicking than I can count, and some early brick paver designs with large voids fell afoul of some of the ADA revenue lawyers, but that was even with perfect installation.

                              • Then why is it that when slate sidewalks were replaced here in New Orleans the contractors laid pressed concrete made and tinted to look like slate? Fear of litigation or federal action because of the Americans with Disabilities Act.

                          • Pavers are great, but they cost a fortune. My area seems to be a heck of a lot more expensive than Chuck's. Around here a full depth asphalt pavement will run you about $6/SF. Brick pavers are more like $19/SF. They do a great job of traffic calming AND do a magnificent job of reducing and filtering urban runoff too. But beyond the initial cost, pavers require much more careful snow plowing than most municipal public works departments can seem to handle. You really shouldn't use the bare steel plow edge that you do on concrete or asphalt or it catches corners and breaks or dislodges the pavers. They make special rubber plow wear edges that are friendlier to pavers, but (again), $$$$. On the other hand a good permeable paver system requires MUCH less salt than asphalt does because they rarely experience re-freeze, which is much of the hazard salt is intended to prevent. If it's warm enough to melt, its gone below the paver and into the underdrain systems before refreeze can happen. But if the QC by the paver manufacturer isn't perfect, freeze/thaw will literally melt these things back into sand after a few years (seen it happen many times).
                            I suspect we will be seeing more of them on low speed roadways in the near to medium future. Car-oriented people hate them because they are unpleasant to drive fast on and because they cost so much more. Once more and more people start experiencing salt-contaminated drinking wells, we might start to rethink how "cheap" salted asphalt roadways are though. Usually that's what it takes to get change.

                              • That's interesting to hear, thank you for all the information! I'm thinking of pushing for more brick paved streets here in our downtown and older residential areas, and have been wondering what pushback we might get.

                                We do have one brick paved street here that is pretty popular, but I'm not sure if it uses full sized bricks or just a thinner overlay, or if it has proper drainage like you suggest. I'll have to ask our city engineer for more details, as well as his experience with them.

                                I do know that the public works department in Kansas City put out an info sheet a number of years ago about the long term cost of paved streets actually coming out ahead of asphalt due to their incredibly long replacement cycle, but that was over the course of a century, which may be hard to swing in your average election cycle.

                                  • Probably the best way to get engineer support for brick pavers when money is scarce (which is always when it comes to road MAINTENANCE budgets) is to focus first on areas that have significant drainage problems or known combined sewer overflow problems and/or known badly undersized sewers. A complete road reconstruction with permeable brick pavers will create a large amount of void volume in the stone underlying the bricks such that very little rainwater runoff occurs for most storms. This innately ups the performance of any existing storm sewers and vastly slows down the rate at which water enters those sewers (mostly trickling thru underdrains after the storm is gone). But the up-front costs of initial construction and public works snow plowing equipment / procedures change is a tough nut to crack. I'm not sure I really believe the total life cycle costs are lower, actually. Modern concrete brick pavers are not the antique cobblestones of old. Most don't have the lifespan of the old stuff. The reasons for that are mostly in differences in how portland cement is made today compared to 100 years ago. That's another long story, but the short of it is that the old stuff took a long time to gain strength after pouring so they used more of it and it kept on gaining strength for months after pouring. Today's stuff gets to its ultimate strength in less than a month and a half. Engineers base designs on the 14 or 28 day strength of concrete so the end result is lower ultimate strength today than in the past.

                              • City officials: "We can't move the curb. *something* *something* drains!"


                                  • The photo of the construction site appears to show a curb extended towards the center of the street, apparently with a height difference of about two inches above the roadway surface.
                                    That can be deadly for bicyclists.
                                    Given bicyclists' propensity to ride to the right edge of the road (despite our efforts to explain why they're safer in a much more leftward position), that sets them up for a "diversion fall." The front tire nudges the curb, and the front wheel is knocked sideways. The rider goes down, hard. (It's the same crash type as when you ride over train tracks at a shallow angle, and the train tracks knock your front wheel sideways.)
                                    It's not clear from the photo what the finished street will look like, but gutter pan seams are significant hazards to bicyclists, even without much height difference.
                                    All that said, we love slow, narrow streets -- and empowering bicyclists to ride in the middle of the lane, where the visibility is greatest and hazards the fewest.

                                      • I used to be a residential engineer on road and bridge projects and with my experience the streets are designed so that the finished surface of the street is flush with the surface of the gutter pan. The only times the gutter pan would pose a hazard is during the initial construction after the bituminous concrete pavement base course is laid but the surface course is not yet laid down, and during maintenance projects during the time between the initial cold-planing (milling) and the resurfacing.

                                          • Not sure which picture you are looking at, but it's typical for asphalt to go down in layers such that the final layer is only about 1.5" thick. That surface layer is made with the smallest stone content so that the surface is smooth and rides quietly (for cars, that is).

                                            • Chris Koch 10 days ago

                                              Great article! Not just for rebuilding existing streets but also for designing new subdivisions. But please close the loop by clearly explaining how the street redesign satisfies the Fire Department's needs to get to fires/accidents/incidents as fast as possible, provide adequate clear width to deploy outriggers for aerial apparatus (eliminate street parking), and minimize aerial obstructions (eliminate street trees or only allow small ones) when they need to deploy aerial apparatus to fight fire from above. From your perspective, how is it in the Fire Department's best interest to be supportive of narrow streets and large street trees?

                                                • The fire department doesn't need to get where they're going "as fast as possible." That's literally prioritizing speed over everything else. The fire truck needs to get places reasonably quickly, though.

                                                  Yes, on the edge, somewhere someone will die who wouldn't have had the fire truck or ambulance arrived a minute, or ten seconds, or even one second earlier, but you can't look at that in a vacuum. If faster response times save ten lives at the destination every year, but the wider streets kill twenty additional people, that's a net loss.

                                                  • Rob 10 days ago edited

                                                    Look at Charles with his fancy streets with a curb!

                                                    Okay, my current neighborhood has one too, but for a good 80+% of my life, I lived on streets without a curb. The street ended and grass started.

                                                    Edit: Also no sidewalks. If you walked, you walked on the street.