Anti-urban groups fight to keep Drake congested

MAD: Fighting to make its logo a reality. Image from MAD. [1]

Despite years of arguing new housing will exacerbate traffic congestion and blaming the county’s urbanists for indifference to the problem of congestion, Marin Against Density (MAD) is now fighting against new traffic lanes on Sir Francis Drake (Drake), arguing the project will actually reduce capacity. Fact check: it won’t.

The project

Drake Boulevard is a mess south of Ross from every perspective. To people on foot or bike, it’s a hot, loud, dangerous traffic sewer. To people in cars, it’s a congested nightmare every rush hour. Thankfully, there’s enough space on the road to make the first problem a little less bad and fix the second problem.*

The biggest change to Drake would be a third lane heading south from Marin Catholic to 101 and, in one design, north from 101 to El Portal by narrowing lanes from between 15 and 21 feet to a standard 11 feet. This will increase capacity by about 50 percent along the most congestion stretches of the road, a huge boost for drivers that have complained about for years.

Other changes would be squaring off intersections in a few sections to make it safer to walk, new shoulders – formerly Class II bike lanes – and wider sidewalks [2]. Given that there are schools along the route, these are victories for parents and children along the way.

So what’s the problem?

According to an email from MAD [3], and to comments from anti-urbanists from the last time I tackled this problem in November [4], the primary complaint is that narrowing lanes will reduce capacity by slowing traffic. They’ve labelled it a traffic calming exercise, designed to support safety rather than traffic flow.

Even if we look past the morally reprehensible attitude that the safety of people walking isn’t worth protecting, it’s utterly illogical. MAD doesn’t understand how roads work.

A short primer on road capacity functions is in the notes, if you’re interested, but here’s the short of it: moving from a 12-foot lane to an 11-foot lane will decrease the free-flow speed of a road by about 3 percent, but adding a whole new lane will increase capacity much more than what’s lost by that very slight depression in free-flow speed. Add it all up, and the project should boost capacity by 45.5 percent.

But what about right-turn lanes lost? There is still more road capacity, so while the far right lanes might be slower during off-peak times, through drivers who won’t be in the far right lanes won’t need to worry.

To put it very simply, the county wants to slow uncongested travelers by about 3 percent to add 50 percent capacity. This seems like the kind of project MAD would support if it was so worried about traffic.

But MAD’s opposition to adding makes so little sense it boggles the mind. Why would an organization that argued any new homes will cause congestion fight against measures that might actually reduce congestion? The political answer might be the easiest.

It’s an election season, and that Fairfax email was rife with disparaging words for incumbent supervisor Katie Rice and glowing words for the conservative, Kevin Haroff, who has come out against the project [5]. By painting this redesign as a road diet rather than the road widening it is, MAD and its fellow organizations (CVP and Citizen Marin) can say that Rice has no solutions and is beholden to the madness of us urbanists.

If it’s about politics, then MAD is lying about the project to help their candidate and Haroff is complicit in the deception.

Of course, lots of anti-urbanists see a conspiracy to destroy Marin’s character. They probably actually believe that adding bike lanes is just part of that conspiracy. Al Dugan thinks I work for an anti-Marin lobbying group in DC, for instance.

So some people are playing the political game and don’t care if they’re on the technically correct side of a given issue or not as long as their candidate wins. Others want their candidate to win because they think only by cleaning house can they halt the spread of dangerous ideas in Marin. It’s a potent mix, and it‘s leading Marin down a dark path.

If even a project that will boost traffic capacity by nearly 50 percent is successfully painted as a congestion-causing project, there’s something seriously wrong with our politics. When we can’t even agree on what’s real or not, we cannot have a successful government. Fairfax went through this during Frank Egger’s years on the council. San Anselmo is going through its own turmoil with Ford Greene. Sausalito and Marinwood are going through phases when the whole governing body is dominated by people who take this sort of confrontational and personal approach to governing.

The Drake project has its problems, and I’ve highlighted them before, but as a symbol of our political dysfunction it is extremely worrying.


* For today, I’m not going to get into induced demand and the Fundamental Law of Traffic Congestion, which Connor Jones went over this past winter [6]. That’s a deeper problem, but fixing it is something nobody has the political stomach to take on even in San Francisco, let alone Marin.

Level of Service diagram, click to enlarge. Image from Wali Mamon.

** Traffic capacity – how many vehicles a road can carry in an hour – is a function of a road’s design speed and the road’s traffic jam density, or how many vehicles fit per mile when traffic speeds are basically zero:

Maximum Capacity = Number of Lanes × ((Free-flow Speed×Jam Density)/4)

This is called the Greenshields model, which is a reasonable tool for analyzing roads like this. Among other things, it tells us that as speed decreases, the number of cars the road can move per hour actually increases, at least up to a point. This is thanks to the fact that the space between cars decreases as speed decreases, allowing the road to be used more efficiently. Generally speaking, this is around Level of Service (LOS) grade E, though engineers try to keep LOS at around C or D to ensure some slack in the system [7].

According to this model, reducing the free-flow speed by 3 percent in this model to add a new lane will increase the maximum capacity by roughly 45.5 percent.

Works Cited

[1] Marin Against Density, MAD Logo, Digital Image, n.d.

[2] Kentfield Planning Advisory Board, “Sir Francis Drake Boulevard Corridor Rehabilitation” (Kentfield, CA, October 28, 2015).

[3] Marin Against Density, “Attend June 1 ‘Open House’ -- Forward This to Friends.,” June 1, 2016.

[4] David Edmondson, “Build Something Better on South Sir Francis Drake,” The Greater Marin, November 18, 2015.

[5] Issues,” Kevin Haroff for Supervisor District 2, accessed June 2, 2016.

[6] Connor Jones, “The Street Economics of Induced Demand,The Greater Marin, December 21, 2015; Connor Jones, “The Four Biggest Myths about Induced Demand,” The Greater Marin, January 4, 2016.

[7] Francis Vanek et al., Sustainable Transportation Systems Engineering: Evaluation & Implementation (New York: McGraw-Hill Education, 2014), chap. 7; Wali Memon, “Highway Level of Service,” October 12, 2012.

A case for the comprehensive bike network

A couple of weeks ago, commenters were largely negative to the idea of protected bicycle lanes on Sir Francis Drake Boulevard for safety reasons and for the reason that the Corte Madera path already existed. But why should we build protected bicycle lanes along high-speed corridors at all? The weight of evidence says it would be of great benefit to cycling in the county generally and to our high-speed corridors specifically.

Network effects

In the Kentfield-Greenbrae corridor, the cycling network is incomplete. The Corte Madera Creek path is a wonderful segment of that network, but it only works for some people. For anyone living north of Sir Francis Drake – yes, there are plenty of flat, bike-friendly streets – that path is useless for getting around the neighborhood. Often, staying off Sir Francis Drake doubles trip times, something no driver would be willing to do.

This holds true for other corridors, and it’s not surprising. Since the rise of the car, arterial roads have become the backbone of our commercial economy. Quiet streets are saved for our showpiece downtowns and residential neighborhoods while high-speed roads serve our everyday shops, like supermarkets, banks, retailers, doctor’s offices, post offices, coffee shops, and the like. By pushing bikes off the high-speed streets, we effectively take biking off the list of acceptable ways to get around for everyday errands.

And there are the benefits of network effects. Though each individual project might not add much to bike ridership, building a complete network will mean every completed segment will add to the usefulness of every other segment. One fax machine is a paperweight. A fax machine in every office, however, makes that one machine very useful. A new safe bike lane on Sir Francis Drake is useful to those living near it. Another one on Corte Madera’s Tamalpais Avenue is useful to those living near that street.

Add a link to Redwood Highway and suddenly you have a network, making both Tamalpais Avenue, Redwood Highway, and Sir Francis Drake useful to anyone along any of those routes while also adding value to the Corte Madera Creek path and the Sandra Marker trail. Any other links – like Bon Air Road or San Anselmo’s Red Hill Avenue – expand the capabilities of the formerly isolated segments even further.

This is backed up by research. Jessica Schoner and David Levinson of the University of Minnesota found that “connectivity and directness are important factors in predicting bicycle commuting after controlling for demographic variables and the size of the city” (Schoner & Levinson, 2014) Since commuting is a minority of trips, and these high-speed roads are also lined with shops and services, the effect on overall trips by bicycle will be larger than expected.

As well, Schoner and Levinson didn’t differentiate between the quality of the bike link, whether it’s a painted bike lane, an off-road path, or a protected lane like what I propose. Other studies (Heinen, Maat, & van Wee, 2011; Tilahun, Levinson, & Krizek, 2007; Wardman, Tight, & Page, 2007) have found that the quality of the bike lane has a meaningful impact on bike-to-work rates; Heinan, Maat & van Wee found this was especially true for short trips. These strongly imply that safer lanes will have a meaningful impact on non-work trips, especially on short trips.

The safety problem

The principal objection to having a protected bicycle lane on a high-speed road was one of safety. Commenter Ann Becker remarked, “A heavily traveled street with traffic going at speeds of up to 40 mph is simply not safe for bike riders, either school age or older.”

Research does not bear out Becker’s assertion. New York City’s Department of Transportation released research indicating traffic collision injuries dropped by an average of 20 percent following the installation of protected bike lanes along major avenues (Miller, 2014), which are often just as unfriendly to people on bikes as Sir Francis Drake. Other studies (Harris et al., 2013; Lusk et al., 2011; Teschke et al., 2012) have found even more significant drops in injury crashes to all road users, including drivers, after the installation of protected bicycle lanes. This holds true even on fast streets like Sir Francis Drake.

All this assumes we agree that bicycling is good for the environment, good for physical and mental health, and good for the economy (Maus, 2012), and it is indeed all those things. Given that a strong network encourages bicycling while also improving road safety, there is no reason to keep protected bicycle lanes off the road, even high-speed roads. As I laid out two weeks ago, we can add protected bicycle lanes to Sir Francis Drake without sacrificing any eastbound lanes. With the heavy weight of evidence, we can further add that this would be of huge benefit to anyone who lives, works, shops, or drives along that boulevard.

Works Cited

In keeping with my university's standards, future blog posts will use in-text citations and a works cited. Often, these will be behind a paywall; please email me at if you would like the full text.

Harris, M. A., Reynolds, C. C. O., Winters, M., Cripton, P. A., Shen, H., Chipman, M. L., … Teschke, K. (2013). Comparing the effects of infrastructure on bicycling injury at intersections and non-intersections using a case–crossover design. Injury Prevention, 19(5), 303–310.

Heinen, E., Maat, K., & van Wee, B. (2011). The role of attitudes toward characteristics of bicycle commuting on the choice to cycle to work over various distances. Transportation Research Part D: Transport and Environment, 16(2), 102–109.

Lusk, A. C., Furth, P. G., Morency, P., Miranda-Moreno, L. F., Willett, W. C., & Dennerlein, J. T. (2011). Risk of injury for bicycling on cycle tracks versus in the street. Injury Prevention, ip.2010.028696.

Maus, J. (2012, July 6). Study shows biking customers spend more. Retrieved from

Miller, S. (2014, September 5). New DOT Report: Protected Bike Lanes Improve Safety for Everyone. Retrieved from

Schoner, J. E., & Levinson, D. M. (2014). The missing link: bicycle infrastructure networks and ridership in 74 US cities. Transportation, 41(6), 1187–1204.

Teschke, K., Harris, M. A., Reynolds, C. C. O., Winters, M., Babul, S., Chipman, M., … Cripton, P. A. (2012). Route infrastructure and the risk of injuries to bicyclists: a case-crossover study. American Journal of Public Health, 102(12), 2336–2343.

Tilahun, N. Y., Levinson, D. M., & Krizek, K. J. (2007). Trails, lanes, or traffic: Valuing bicycle facilities with an adaptive stated preference survey. Transportation Research Part A: Policy and Practice, 41(4), 287–301.

Wardman, M., Tight, M., & Page, M. (2007). Factors influencing the propensity to cycle to work. Transportation Research Part A: Policy and Practice, 41(4), 339–350.

Build something better on South Sir Francis Drake

Tonight, the county will hold a hearing on rebuilding and enhancing Sir Francis Drake Boulevard from the Ross border to Highway 101. (Details: 7pm, College of Marin, Kentfield Campus, Fusselman Hall 120, project site here.) This provides a golden opportunity for Marinites to transform and improve one of Central Marin’s most important streets to better serve people in cars, on bikes, on buses, and on foot.

Congestion sucks

From a workshop survey in late October, people called traffic congestion the worst problem along the corridor, and it’s not hard to see why. Drivers have to deal with stop-and-go traffic all along Bon Air Shopping Center to 101 in the morning, and a number of intersections are overloaded at the same time. This, of course, sucks for drivers and bus riders alike, as well as anyone living, working, or shopping along the corridor.

Walking and biking along Drake is also a pain. As a 35-mph roadway with narrow and sometimes nonexistent sidewalks, it is impossible to feel welcome either on foot or on bike, a major problem for kids and their parents, as well as those who don’t have their own car.

But Sir Francis Drake isn’t just a traffic sewer. North of Bon Air, Drake serves as a main street for Kentfield and College of Marin, and a vital access to Bacich Elementary and Marin Catholic High schools. How to connect these uses together with the high-capacity roadway to the south is a quite challenging question.

Design advice

Though it’s important to lay out priorities before tackling a planning problem, along this corridor the traffic concern is overriding. So, instead of laying out priorities, let’s lay out the tools in our toolbox:

  • Intersection Design
  • Segmenting travel modes
  • Adding car lanes

Each of these will relieve some stress on the roadway, either by improving volume (the second two) or easing traffic flow generally (the first one). We also want to make sure that any additional lanes are consistent – it’s a bad idea to start a lane and then end it.

The presentation in October split up Drake into 4 segments: Ross Limits to Broadway; Broadway to Wolfe Grade; Wolfe Grade to El Portal; and El Portal to 101. Each segment’s right-of-way (property line to property line) is a different width, which makes planning consistently difficult.

Nevertheless, I’m unimpressed by the solutions presented. Unprotected bicycle lanes on a 35mph road will simply never be used. This might be excusable if there weren’t space for buffers, but a huge amount of space is dedicated to a center turning lane and median. As well, 11-foot lane widths, though a huge improvement to the 15-21-foot lanes, are wider than a city street ought to be. Lanes of 10 feet should be standard. For comparison, freeway lanes are generally 12 feet wide.

Here are current conditions, the county’s ideas, and my own ideas. Note that despite having protected bike lanes, there are no proposed eastbound traffic lanes cut, meaning the roadway's throughput will remain enhanced where it is most under pressure.

Segment 1: Ross Limits to Broadway

Hover over each of the following to see commentary.

Segment 2: Broadway to Wolfe Grade

Hover over each of the following to see commentary.

Segment 3a: Marin Catholic

Hover over each of the following to see commentary.

Segment 3b: Bon Air Road to El Portal

Hover over each of the following to see commentary.

Segment 4: El Portal to Highway 101

Hover over each of the following to see commentary.

Protected bike lanes drive bicycling use

The reason I have added protected bicycle lanes to each segment is because they push for a relatively fantastic increase in cycling use. At the moment, just 1 percent of users along Drake are on bike, probably in part because of how difficult it is to bike along the route. Boosting that percentage even a bit - to 5 percent - could do a lot to cut down on traffic, especially around school times.

Congestion is the result of a tipping point, where the traffic levels rise just a bit too much, causing speeds to fall off a cliff. Taking just a few trips off the road can have an outsize effect on congestion levels. When paired with a wider road, as both the county and I propose, it should do wonders to cut down on traffic. The lanes may also soak up some of the induced demand from driving that occurs whenever a road's capacity is increased, prolonging the usefulness of this improvement.

Intersection Design

For each of the proposals I generated, intersections should be redesigned to allow the easy flow of people in all modes. Check out the full presentation for info on the proposed intersections, which do a great job for pedestrians, but they are insufficient for protected bicycle lanes. I've uploaded some options from the NACTO bicycle guide below.

If you're going to go to the meeting at this last minute - I myself only found out about it today - then get yourself to College of Marin at 7pm, Fusselman Hall 120.