This semester, I took a Policy Analysis course as well as a Quantitative Methods course. Since I have an overarching interest in transportation, I decided to thematically tie these two courses together by focusing each of their final projects on the same topic – i.e., looking at ways to reduce traffic congestion in San Francisco. I first did a quantitative analysis on the effect of bike lanes on congestion and then used the results to bolster a policy proposal in a broader investigation into reducing road capacity demand in 2021, reproduced below. [PDF version here]
Traffic congestion in San Francisco has been a longstanding problem. It is also potentially set to worsen in 2021 as people become accustomed to driving individual vehicles and return to work after the COVID-19 pandemic. Unfortunately, congestion has many negative economic and public health consequences for both residents of San Francisco and out-of-town commuters. The goal of this analysis is to identify short-term policy recommendations for SFMTA to mitigate the return of congestion by reducing demand for road capacity in 2021.
Eight criteria are used to evaluate six policy options, initially with a non-dominated alternative method. Effectiveness is measured in potential reduction in vehicle miles traveled (VMT) across the city in a one-year timeframe. Parking pricing, HOV prioritization, and bicycling infrastructure are further refined into a targeted policy package that blends carrots and sticks while also correcting for equity concerns. A scenario analysis is used to compare the expected value of doing nothing versus executing the policy package. The result is a prescription that advocates a phased approach – not rushing to complete major projects in 2021 but identifying concrete actions that SFMTA staff can take to prepare for rapid deployment of prioritized policy elements should the need arise.
Recommendations for monitoring impact include specific guidance for each element in the policy prescription. The analysis concludes with an expectation of reduced VMT in any scenario, but the recognition that there will always be significant opportunities to efficiently reduce VMT on both individual roadways and whole neighborhoods whenever it is desirable.
The Congestion Problem
San Francisco was recently ranked the world’s 5th most congested city (Keeling 2018), with average auto speeds during peak periods slowing by about 30% over the past decade (San Francisco County Transportation Authority 2019). While the COVID-19 pandemic and subsequent remote work policies have temporarily reversed this trend, transportation experts predict that traffic congestion may come back worse as normal work conditions return but people become accustomed to driving individual vehicles instead of taking public transit (Savidge 2020).
Congestion has many adverse effects for those living in San Francisco as well as those commuting into the city for work. It delays trips for both individual drivers and transit riders, makes accidents and injuries more likely, increases air pollution, and increases the cost of doing business to the point that it limits future economic expansion. (Tumlin 2012)
Given the worsening projections of traffic congestion and their known costs on society, cities are motivated to limit the return of congestion as part of the pandemic recovery process. Since the problem of returning traffic is imminent, our goal is to identify short-term (less than one year) policy options that can reduce demand for road capacity, as opposed to building out new road infrastructure (supply). Therefore, how might SFMTA reduce road capacity demand on the streets of San Francisco in 2021?
Eight Evaluation Criteria
We will utilize a blend of traditional criteria and others especially significant to stakeholders in San Francisco to evaluate our policy alternatives.
|Effectiveness||Minimize VMT (Vehicle Miles Traveled) within the boundaries of San Francisco|
|Equity||Support vertical equity – place smaller burdens on residents with less|
|Administrative Feasibility||Have ability to be implemented from an organizational (SFMTA) standpoint|
|Political Feasibility||Have possibility of getting adopted by the San Francisco Board of Supervisors|
|Technical Feasibility||Have ability to be physically implemented on the streets of San Francisco|
|Cost||Financially feasible to pursue|
|Complexity||Easy to understand by stakeholders, particularly the residents of San Francisco|
|Appeal to Merchants||Support the small business community, an especially important stakeholder group to satisfy|
Six Policy Alternatives
The initial set of policy alternatives was developed after conducting a broad literature review on transportation demand management (TDM) strategies and selecting a sample of options that had historic precedence of success in cities similar in size to San Francisco, both in physical area and population. The high number of options and their variations required consolidation for simpler analysis, so packages were created representing broad categories of alternatives. These packages were then refined with feedback from peers after a first round of analysis.
Here we describe the higher-level alternative packages, and in the subsequent analysis we will take a closer look at the potential for mixing a few components of each as part of a final policy prescription.
Introduce Congestion Pricing
Taking a cue from Stockholm’s congestion pricing scheme or Singapore’s Electronic Road Pricing program, San Francisco could implement a fee for drivers who enter the downtown core area during peak hours. This fee could be collected via the same Fastrak transponder devices that drivers currently use to pay bridge tolls, or it could be billed by matching vehicle registration data to images of license plates captured as vehicles enter the congestion pricing zone.
The fee could be programmed to vary depending on the time of day or by measured traffic levels, increasing in parallel with congestion. Low-income or other disadvantaged groups could have special tags or programmed transponders that offer a percentage discount on the fee.
The revenue from the fee could be reinvested by SFTMA to improve transit service, ensuring there are good transportation alternatives for drivers who opt out of driving. The revenue could also be a funding source for a complementary policy idea called Congestion-Clearing Payments to Passengers, where drivers receive financial compensation for becoming a passenger in a congestion-reducing mode. (Minett, et al. 2020)
Increase Parking Pricing
San Francisco already has parking meters with dynamic pricing along many downtown streets. SFPark could program these to increase the cost of parking at peak commuting hours to create a disincentive for driving into the area during these highly congested times. (Tumlin 2012) To reduce congestion more drastically throughout the day, the city can increase prices for daily parking across all its public garages and eliminate monthly passes that cap these costs for drivers. (Victoria Transport Policy Institute 2019) Parking prices should be set high enough such that at least 10% of parking spaces are unoccupied at any given time. (Shoup 2006)
The increased revenue, like that from congestion pricing, can be used to fund improvements to public transportation and other programs that support non-congesting modes.
Prioritize High-Occupancy Vehicles (Transit-Only Lanes)
SFMTA could reconfigure some of the most highly congested roadways to create priority lanes for buses, at the expense of lanes for car traffic and/or parking spaces. Special, dedicated lanes for buses could evolve into a highly efficient and reliable Bus Rapid Transit (BRT) service in the future.
While it may seem that the lanes taken away from automobile traffic would lead to increased congestion, the result may be the opposite. The Law of Induced Demand indicates that as more capacity on roadways is added, the more traffic naturally arrives to consume it. (Litman, Generated Traffic and Induced Travel 2001) This policy option attempts to leverage this in reverse, removing capacity to temper the level of traffic demand overall. Congestion may spike in the short-term but should reduce as drivers are discouraged from utilizing the affected roads.
Install bicycling infrastructure
New bike lanes could be woven into San Francisco’s existing bike network and could become increasingly popular as more people seek open-air commuting options. Facilities for bicycling are commonly installed on city roadways as part of a Complete Streets Policy. (Smart Growth America 2018) Many types of bicycling facilities are possible, ranging from simple trails all the way to grade-separated bikeways. (Victoria Transport Policy Institute 2019) However, a quantitative analysis by this author comparing the mean auto speeds of roadways in San Francisco with different types of bicycling infrastructure found that dedicated bike lanes would be a preferable option to bike routes where traffic is shared between drivers and cyclists.
Package of Employer Benefits
San Francisco could put together a package of expanded incentives for commuters to switch to non-congesting modes of transportation, mostly paid for by employers. Universal transit passes that allow unlimited rides on SFMTA could be sold to employers (through a program such as WageWorks) who would then be able to claim the cost as a tax deduction. Parking Cash-Out is a concept that would force employers to offer a transportation fringe benefit to employees equal to the value of free or reduced-price parking. (Tumlin 2012) Subsidization of carpooling services such as Scoop could also be rewarded with tax incentives from the city.
Supporting these benefits would cost the city some tax revenue but would provide more stable funding to transit agencies (through guaranteed purchases of passes). Shifting more employees away from driving could also open the possibility of reduced parking requirements for real estate developers, which would in turn reduce the costs of commercial leases for employers. (Black 2010)
SFMTA can make a wager that the trends in traffic congestion will not continue in their current trajectory, and not take any specific action to address it. This may be the case if remote work becomes permanent for a significant portion of the population or the region experiences an accelerated exodus of residents as people seek more affordable housing elsewhere.
Setting Baseline VMT
In order to set a baseline for what congestion might look like in the “Do Nothing” scenario, we can look at the trends for auto speeds and VMT in San Francisco prior to the COVID-19 pandemic as well as in the timeframe starting at the point where stay-at-home orders expired.
Sources: (San Francisco Municipal Transportation Agency 2019, Tischler 2018)
We can see that average speeds on San Francisco roads have been declining over the past decade, settling into a new low in recent years. VMT has been more volatile (dipping at times of recession) but has started a significant uptick. Unfortunately, the annual data on these key measures is absent in 2018 and onwards. Other sources provide more recent data broken down more granularly.
Sources: (Markezich 2020, San Francisco County Transportation Authority 2020)
It seems that San Francisco has not yet returned to pre-pandemic levels of VMT as of November 2020, which makes sense as most remote work policies are still in place. Assuming traffic recovers to 100% of its former peak, we should expect about 10 million vehicle miles traveled per day in 2021.
Measuring Effectiveness in Reducing VMT
For each policy alternative, we can estimate their effectiveness in reducing VMT or improving auto speeds using historical precedents and prior research.
In Stockholm, a congestion pricing trial had caused vehicle trips to fall by 22% after six months. (Tumlin 2012) London’s Congestion Scheme seems to have been responsible for an 18% decrease in vehicles entering the congestion-free zone. Singapore’s initiation of their ERP program resulted in an additional 15% decline in traffic volumes on top of the previous ALS program. (Black 2010)
The San Francisco County Transportation Authority appears to be targeting a 15% reduction in downtown car trips during rush hour in the scenario planning work they have done. Hence, we will assume a 15% reduction in VMT for this policy alternative.
Transportation elasticity studies have shown that modest increases in the price of parking can have significant effects on vehicle travel patterns. One estimate is that a 10% increase in parking charges reduces vehicle trips by 1-3%. (Willson 2015) Another study found that increasing parking fees from $0.28 to $1.19 per hour reduced VMT by 11.5% (Victoria Transport Policy Institute 2019)
Given that the impact on VMT can vary greatly depending on the scale of the price increases, we can make a simplifying assumption that San Francisco could raise prices around 35% to target a 10% reduction in VMT.
HOV Prioritization (Transit-Only Lanes)
The primary benefit of introducing dedicated lanes for buses is the increase in total person throughput on a given roadway. In this sense, VMT reduction will be attained by way of individual drivers choosing these alternative modes of transportation once it becomes clear they result in faster trips. The switching from single-occupancy vehicles to other modes has been studied for effects on vehicle trips, with results varying from a reduction of 1.4% to 30% depending on how the lane is configured. (Victoria Transport Policy Institute 2019)
For this analysis, we can make a conservative estimate of a 5% overall reduction in VMT given that these improvements will roll out slowly over time, and only on certain roadways in San Francisco where it is easiest or most feasible to make such changes.
Similar to HOV prioritization, adding dedicated bike lanes increases the total person throughput potential of roadways. Historical research has found that adding bikeways and other improvements to cycling conditions leads to increases in bicycle travel and related reductions in vehicle travel. (Clifton, et al. 2012) In cities with population greater than 250,000 (which includes San Francisco), adding a mile of bike lanes per square mile is associated with ~1% increase in bicycle commute mode share. (Dill and Carr 2003) However, if bike lanes are introduced on narrow, congested roads with moderate to high speed traffic where cars cannot pass easily, congestion can actually become worse. (Litman, Evaluating Active Transport Benefits and Costs 2020) The hilly nature of San Francisco also limits the appeal of biking to either more athletic commuters or those with the financial means to utilize electric-powered options.
Given the mixed potential effects of bike lanes and slow rollout, we can make a conservative estimate that this policy option would result in a 2% reduction in VMT, notably less effective than HOV prioritization.
Universal transit passes seem to result in an average reduction in car mode share by 11%. (Tumlin 2012) A study of parking cash-out programs in California showed the numbers of workers driving to work alone fell by 17%, with vehicle miles of travel for the firms studied dropping 12%. (Black 2010) A study of employer-based TDM programs in Washington State found an average vehicle trip-reduction of 11.3% due to carpooling discounts alone. (Georggi, et al. 2007)
If we combine these programs and take a conservative estimate of the impact to account for overlap in the benefits, we can say that this policy alternative could result in a ~30% reduction on VMT. However, this would only apply during regular commuting hours, which limits its effectiveness on overall VMT. Since commuting is only about 28% of household VMT (Federal Highway Administration 2015), we should expect only about 8.4% (30% of 28%) overall VMT reduction from employer benefits.
Ranking the Alternatives
Now we can evaluate the policy alternatives against the rest of the chosen criteria, ranking each of them in a Non-dominated Alternative Method. Some commentary on how each of the other criteria were ranked follows.
|Congestion Pricing||Parking Pricing||HOV Priority||Bike Lanes||Employer Benefits||Do Nothing|
|Effectiveness||-15% VMT||-10% VMT||-5% VMT||-2% VMT||-8.4% VMT||-0% VMT|
|Appeal to Merchants||F||E||C||D||A||B|
The benefits of HOV prioritization on equity cannot be overstated. For those San Francisco residents without the means to afford a car, buses may be their only commute option within the city. Giving buses dedicated lanes will result in more reliable service, directly benefiting these historically disadvantaged communities. (SFMTA 2020)
On the other hand, congestion pricing (like bridge tolling) is widely seen as having the potential to hurt individuals who were previously displaced from living within the city limits. For those commuting from more affordable but far-flung satellite cities (e.g. Richmond, Hayward, Antioch, etc.), the lack of reliable transit options means they may be forced to drive for a reasonable daily commute time. Charging a flat fee to enter the downtown area would be disproportionately more difficult for this disadvantaged group. An across-the-board increase in parking prices would hurt the same people in a similar fashion.
Putting together a package of employer benefits such as unlimited transit passes or carpool subsidies would be the most difficult from an administrative standpoint. The city would need to contract with a provider such as WageWorks to implement the desired benefits and calculate the tax subsidy required for the employers. Training and educational materials would need to be produced to help both employers and employees understand the program options. Finally, record-keeping about which employers are participating and the programs they choose to implement would be necessary.
Comparatively, a proposal to increase parking pricing would be much simpler to implement, since existing infrastructure and systems exist to monitor/collect/modify parking fees. This is not quite as true for congestion pricing, which would need administrative work to define boundaries, effective hours, and enforcement methods.
Congestion pricing is notoriously controversial in the United States. As an example, the concept was first proposed in New York City in 2007, with rollout now planned as late as 2023. Opposition from lobbying groups such as AAA and local neighborhood advocacy groups in the outer boroughs have stalled progress with concerns about the potential effects on businesses and long-range commuters. (Colon 2020)
In San Francisco, doubts about the return of traffic and concerns about equity have also made for difficult political maneuvering. SFCTA has put out a survey for feedback and expects plenty of input from community groups. (Matier 2020)
In contrast, employer commuter benefits are seen as a win-win-win solution – addressing peak-time congestion, giving employers valuable tax deductions, and giving employees extra non-taxable job perks.
Technical Feasibility & Cost
Similar to administrative feasibility, programs such as employer benefits and congestion pricing would be more difficult to implement while increasing parking pricing would be relatively trivial. While existing Fastrak transponders could be used as tracking devices for congestion pricing, significant work would be required to add receivers and cameras to all of the streets leading into a congestion zone.
In these two criteria, adding HOV priority lanes would be relatively easier than bike lanes because no lane widths would need to be changed. In order to build effective separated bike lanes, major street redesigns are often required. (E.g. street parking had to be completely reconfigured to accommodate a new bike lane on 2nd Street.)
Explaining an increase in parking pricing to San Francisco residents and commuters would be relatively easy. However, significant efforts in education and marketing would be necessary for programs such as congestion pricing and employer benefits.
Bike lanes are very common and familiar to people across San Francisco while there are only a handful of existing transit-only lanes. In addition, the regulations around transit-only lanes allow for certain other types of vehicles that are not strictly public transit, which leads to confusion among residents. (Vaughan 2020)
Appeal to Merchants
The small business community generally fears any initiative that would disincentive customers from visiting their neighborhoods – for motorists in particular, as they are perceived as comprising the majority of existing city visitors. Hence, proposals such as congestion pricing or increasing the cost of parking will be extremely unfavorable amongst this community. Instead, employer benefit programs are favored as they would also provide financial incentive to the employers to participate.
Eliminating Alternatives and Zooming In on Others
Congestion pricing clearly has the most potential effectiveness if implemented (resulting in a reduction of 15% of 10M, or 1.5M vehicle miles traveled). Unfortunately, the ranking exercise revealed significant downsides in all other criteria. Employer Benefits likewise had promising effectiveness but suffers too much in feasibility, cost, and complexity to warrant a recommendation. Hence, these two alternatives will not be considered further.
On the other side of the spectrum, doing nothing would result in no VMT savings, but would satisfy almost all other criteria. We will revisit this option in a scenario analysis later.
HOV Prioritization and Bicycling Infrastructure were the most middle-of-the-road alternatives, resulting in a modest number of VMT saved (500K and 200K, respectively) while reasonably weighted in all other criteria. It may be possible to combine some elements of these alternatives with a modified parking pricing proposal that avoids the negative aspects of equity, political feasibility, and appeal to merchants.
Targeted approaches to HOV prioritization & bicycling infrastructure
SFMTA has a comprehensive Equity Strategy (SFMTA 2018) that identifies 8 neighborhoods to focus on based on demographics. These would be ideal locations for new transit-priority lanes where they don’t exist already. When comparing against a map of planned transit priority projects, it seems that the Bayview neighborhood could use some attention in particular. Planned projects in the Outer Mission/Excelsior and Visitacion Valley neighborhoods should also take priority over others if possible.
Source: (SFMTA 2018)
We can also take a closer look at which streets are seeing the fastest return of congestion, based on VMT change relative to pre-COVID levels. Based on this data, it seems there are a number of east-west streets in the North of Panhandle, Western Addition, Lower Pacific Heights, and Japantown neighborhoods that are of particular concern. Comparing this with SFMTA’s Bike Network map, we can see the potential for new additional dedicated bike lanes and/or conversion of shared bike routes into separated bike lanes.
Source: (SFCTA 2020, SFMTA 2020)
These targeted approaches to HOV prioritization and bike infrastructure would magnify their strengths and limit their weaknesses (i.e. feasibility and cost, which generally scale based on scope).
Looking closer at parking pricing
Parking management is most successful when it is comprehensive (addressing the full range of parkers’ experiences) and coordinated (between parties controlling parking resources). It is also easier to execute when paired with improvements to alternative transportation options such as the dedicated bus and bike lanes discussed above. (Willson 2015)
Simply increasing parking prices across the board is appealing due to the low cost and complexity, but it does suffer the risk of hurting merchants and broader social equity goals. Hence, we should look into potential variations on this policy option to mitigate these concerns.
One idea is to differentiate prices based on origin-destination pairs, factoring in area demographics and availability of alternative transportation options. (Gallo 2018) This would require more sophisticated tracking mechanisms, however, which would negate the ease of implementation benefits. A simpler variant would be to not increase pricing as severely in neighborhoods that primarily draw low- and middle-income clientele – in other words, linking price increases to the average price of a shopping trip in a given area. (Ma 2019)
Yet another option would be only to increase parking rates within city-owned garages and offer special reduced-rate permits for low-income workers. The Portland Bureau of Transportation did this to alleviate stakeholder concerns when they introduced new downtown on-street parking rates. (Portlanders for Parking Reform 2016) This idea could be combined with an effort by the city to lease parking spaces owned by merchants, guaranteeing them some revenue while taking control of pricing for these advanced techniques. (Willson 2015)
The value of doing nothing
As seen in the ranking of alternatives, there is a lot of appeal in doing nothing. This is especially true as SFMTA is experiencing a massive budget shortfall due to plummeting transit ridership, so funding availability for new initiatives is in short supply. It is worth exploring a few potential future scenarios and their expected values of VMT reduction overall, for example:
- Scenario 1: Everything goes back to normal immediately after the COVID-19 vaccine is made available in 2021 and baseline VMT is reset at 100% of pre-pandemic levels
- Scenario 2: The effects of the pandemic lead to a prolonged recession while remote work becomes more mainstream, hence VMT stays at 80% of pre-pandemic levels indefinitely
- Scenario 3: The economy comes roaring back and people end up commuting more with their cars due to a sustained unease with public transit, so VMT skyrockets to 120% of pre-pandemic levels
Given the existing trends seen in daily VMT as well as noticing how VMT dips in San Francisco for a prolonged number of years after each recessionary period (see baseline figures above), it would seem that Scenario 2 is actually more likely than the others. If this is the case, then we can place a higher probability on that outcome and calculate the resulting VMT for each Scenario (starting from a baseline of 10M) if no policy action is taken versus the package of parking pricing, HOV prioritization, and bike lanes implemented with the suggested modifications discussed above.
|Scenario||VMT levels in 2021||Probability||Outcome of Doing Nothing||Outcome of Targeted Policy Action (-17% new VMT)|
|1||100%||20%||-0 VMT||-1.7M VMT|
|2||80%||50%||-200K VMT||-3.36M VMT|
|3||120%||30%||+200K VMT||-0.04M VMT|
|Total Expected Value||-160K VMT||-2.032M VMT|
Of course, targeted policy action would always result in a much more significant expected reduction in VMT, but it’s important to note that the expected value of doing nothing is still negative. (This would hold true as long as we place a higher probability of Scenario 2 over Scenario 3.) Hence, if a very slight reduction in VMT is acceptable in the short run, doing nothing may be actually the wisest course of action.
Final Policy Prescription: A Phased Approach
Our targeted policy package is a blend of both carrots and sticks: HOV prioritization (transit-only lanes in Equity Neighborhoods) and more dedicated bike lanes along congested corridors to encourage alternatives to single-occupancy vehicle use, with focused increases in parking pricing to make it more painful for those who still want to drive directly into the priciest areas. Together, the potential reduction of over 2M VMT from this proposal makes it very appealing.
However, we have also seen that doing nothing can also be expected to reduce VMT (albeit quite modestly) without any of the potential costs and feasibility downsides. In a pandemic year with a budget crisis at the SFMTA, this option warrants serious consideration.
Ultimately, the question becomes whether the problem of returning congestion is as urgent as first thought. Given the context and the low risk of doing nothing, the immediate recommendation would be to not rush into trying to complete any new projects in 2021. Rather, SFMTA could take the time to start laying the groundwork for the targeted policy alternatives while closely monitoring congestion levels for any signal that they might exceed 100% of pre-pandemic levels.
Specifically, SFMTA staff could:
- Begin identifying corridors for transit priority and bike lanes based on equity and traffic patterns
- Start gauging community interest as part of existing work in those areas
- Continue meeting with the SF Board of Supervisors and keep them informed about what they’re seeing, building up political support for these ideas
- Negotiating parking leases from merchants if they see some with unused capacity
Should traffic congestion spike in 2021, certain elements of policies should be implemented faster than others. For example, increasing parking garage pricing would be a good first step since it has the highest potential effectiveness. Then, transit-only lanes could be implemented on an ‘emergency’ basis with temporary street modifications, with a standardized way of making them permanent in the long-term. Bike lanes could be added later on, given their increased design cost and limited effectiveness.
With this more cautious and phased approach, SFMTA can manage their limited budget while also not blindly accepting congestion as inevitable.
Monitoring and Measuring Success
Fortunately, SFCTA is already actively monitoring citywide VMT as well as congestion levels on select roadways. They would need to expand this, however, if SFMTA ends up planning interventions on certain roads not already measured. This close partnership would need to be nurtured for a truly complete ex-post evaluation of the effectiveness of the policy proposals.
The effectiveness of various elements of the policy recommendation would need to be measured in slightly different ways. While the effects of roadway modifications like transit-only lanes and bicycling infrastructure can be measured with auto speeds during peak periods on the specific roadways directly, the effects of proposals like parking pricing adjustments affect broader areas so they would need to be measured on a neighborhood basis. For example, SFCTA could report on the average percentage change of auto speeds during peak periods for a set of roadways within a 2-mile range of a parking garage that experienced price increases.
The success of this policy prescription lies in several dimensions. First, stakeholders including SFMTA, SF residents, merchants, and the Board of Supervisors would need to be consulted to determine whether they believe this was a thorough and complete analysis of the space. Then, we can check to see whether the recommendations were ultimately adopted – specifically in the phased approach described. Finally, we can evaluate the actual levels of VMT after 2021 to see the impact of the targeted policy alternatives. We would expect a reduction in VMT in any scenario, but we can conduct more scoped studies to show how certain roadways or neighborhoods benefited from the interventions proposed. In this manner, we hope that SFMTA succeeds in reducing road capacity demand in San Francisco – one way or the other.
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