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New Mace Blvd Traffic Study Needed Before Making any More Changes

ChangePicby Alan Pryor

The City is in the midst of trying to formulate a plan to alleviate traffic congestion along the Mace Blvd. Corridor.

Following are excerpts from the Staff  Report presented to the Bicycling, Transportation, and Street Safety Commission (BT&SSC) for their July 11, 2019 meeting which discusses the traffic congestion on Mace Blvd and the City’s proposed responses.

Traffic Congestion:

Since the project design phase was completed in 2016 and prior to construction, traffic congestion steadily increased along the corridor during the evening peaks, particularly on Thursdays and Fridays. Several factors have converged which explain this condition:

  • Traffic congestion on eastbound Interstate 80 backs up past the Downtown/Richards Blvd exit, sometimes west of State Route 113, resulting in motorists exiting at the Richards off-ramp, bypassing freeway congestion by traveling east on Chiles Road through Mace Blvd, which increases congestion at the Mace Blvd/Chiles Road intersection.
  • The Mace Blvd on-ramps to eastbound Interstate 80 back up, increasing congestion.
  • Mobile and in-car navigation applications re-route freeway traffic in Dixon at the Pedrick Road interchange around the congestion via eastbound Tremont Road and northbound Mace Blvd.”

Whether the fault lies solely in the increased traffic on I-80 or diversions through Davis or the City’s failure to anticipate and account for it is a moot point at this stage. Clearly, the next step must be to get an accurate handle on what traffic flow patterns are now and how they will change in the future. Unfortunately, there is nothing in the Staff Report that provides current estimates of daily and peak traffic counts and how they will change in the future except to say that it will get worse.

“Traffic congestion on Interstate 80 continues to increase, as does the use of navigation applications diverting drivers around it. This technology has also affected Cowell Blvd, Covell Blvd, and Second Street corridors. Given navigation algorithms route drivers based on travel time, peak traffic congestion relief from capacity-increasing design revisions may not endure, long term. That is, routing more cars through the corridor may occur, resulting in similar congestion problems.

Therefore, adjustments to the Mace Blvd corridor should focus on accommodating local traffic demands and movements, while assisting with alleviating out of town “cut through” traffic to the extent possible. Ultimately, the solution rests with either capacity increases on Interstate 80 or other policies to bring highway travel in better alignment with capacity. Separate efforts with Caltrans are underway to examine this issue more closely.”

Any changes in traffic flow in I-80 that may alleviate the congestion problem on Mace are at least a decade ahead of us. CALTRANS might be able to put in some High Occupancy Vehicle (HOV) lanes within a 5-year period . But this will only help commuters that carpool get to the bypass a little more quickly. It will do nothing to alleviate the main source of congestion on I-80 which is the bottleneck at the Yolo Bypass Causeway. I’d venture to say that any work to add additional lanes to the Causeway will be at least 10-15 years in the future.

So I believe the City would be foolhardy to just try to solve traffic problems on Mace only by “accommodating local traffic demands and movements, while assisting with alleviating out of town “cut through” traffic to the extent possible” while otherwise praying that CALTRANS can solve the I-80 congestion problem. This is a short-sighted plan especially if the proposed fixes are implemented without a thoroughly vetted updated Traffic Study.

Toward encouraging such an updated traffic study, that end, I submitted the following letter to the Bicycle, Transportation, and Street Safety Commission (BT&SSC) and the City Council concerning the need for a new traffic study to be done on Mace Blvd before implementing any proposed roadway modifications to alleviate the current congestion problems.


To:    Bicycling, Transportation, and Street Safety Commission & Davis City Council

From: Alan Pryor

Date:  July16

Re:     Need for a New and Updated Traffic Study for the Mace Blvd. Corridor

Dear Commissioners and Council-members - Following is an edited copy of written comments I left with the BT&SSC at their meeting last week.

The Mace Blvd corridor though the I-80 interchange has become the worst street in Davis in terms of traffic delays and motorist frustration. There are now far more strident complaints about this problem than ever arose about Richards Blvd.-Olive Dr. even during the height of the Nishi 1.0 debate when citizen attention was focused on that problem.

I confess I have not been actively involved in the meetings and discussions surrounding possible Mace Blvd. fixes but still wanted to share one observation I had after reading the Staff Report on the proposed upgrades presented at last week’s BT&SSC meeting. It seems the City’s s proposal is to take an iterative approach to solving the problem. That is, one small change will be made and, after seeing how that works, then another small change will be made and see how that works, etc.

However, there seems to be a key component missing from this process and that is having an updated traffic study of the entire corridor done so real traffic numbers are modeled and evaluated when considering future changes. Although the Mace Blvd. improvements were designed in 2015-16, I believe they were based on traffic counts going back to around 2011. I think a prudent course would be for the City to commission a completely new traffic study on the Mace Blvd. corridor before implementing any new changes at all.

Yes, that will cause delays and be time-consuming. But right now I don’t think the City really has a handle on the scope of the current problem much less how bad it might get in the future. And the City itself acknowledges in the Staff Report that traffic has substantially worsened since the design was approved and WILL get worse in the future if only from increased I-80 traffic alone.

But the 800-lb gorilla in the room that is not being considered is the traffic impacts on Mace Blvd. of any new Aggie Research Campus (ARC). The EIR for that project (done when it was still called the Mace Ranch Innovation Center - MRIC) was certified about 3 years ago but it was similarly based on much older traffic counts circa 2011. How will the thousands of daily trips through the Mace Blvd. – I-80 interchange resulting from the ARC project impact the traffic flow on Mace Blvd that has already become enormously more congested in the past 8 years since the traffic counts were originally done?

I would suggest that any new traffic study done to guesstimate impacts on different Mace Blvd. configuration changes must also look to the future by including both increased I-80 traffic AND increased estimates of traffic as a result of the proposed Aggie Research Complex.

By the City's own admission in the Staff Report, traffic through the Mace Blvd corridor and I-80 has substantially increased in recent years which would constitute a change in circumstance from when the old MRIC EIR was certified with the now-dated traffic counts and obsolete traffic study. Therefore, an updated traffic study of the Mace. Blvd. corridor MUST be done anyway to amend the EIR for ARC if only to avoid litigation if the City otherwise proceed with a Notice of Determination for an EIR which relied on the old traffic data.

If a new traffic study has to be done anyway for the ARC proposal which is expected to be brought forward soon, shouldn’t you consider the results of that study before giving your blessing on any short term proposed Mace Blvd. fixes now?

Respectfully submitted,

Alan Pryor


The EIR previously certified by the City for the MRIC project (now ARC) indicated that "Mace Boulevard carries approximately 17,500 vehicles per day according to the traffic counts collected by the City of Davis in April 2011." The EIR also projected that the commercial-only (no housing) option "would generate about 2,600 AM peak hour trips, 2,390 PM peak hour trips, and 17,100 daily trips before considering external trips made by non-auto travel modes." or about doubling the 2011 traffic counts which, by now, are very substantially understated

Clearly adding 17,000 trips per day to the already congested Mace Blvd. corridor could result potentially result in gridlock through the entire Mace Blvd. - I-80 corridor.

The estimates of increased traffic on Mace Blvd. as a result of ARC underscores the need for a thorough and complete traffic study before any short-term fixes are made to Mace Blvd south of Chiles Rd.


Nancy Price

Couldn't agree with more with you both. Thanks Alan and Desmond.


My understanding is that any big modifications to I-80 are ten years out, and that Caltrans only has half the money committed that they need. The main source of congestion is too many people using the highways, also driving alone. The Causeway section is the correct width and number of lanes; it's the rest that's too wide. Prove me wrong with a twinkle in your eye, rather than a scowl of pessimism.

All that said, it's clear that the transportation solution for any version of ARC cannot be the highways, even with buses running on a dedicated lane at commuter peaks.

Going back to the present say, Supervisor Provenza needs to stay at meetings until the end when it's mainly his constituents that are so very entitled - referring to the most recent meeting at Pioneer Elementary. El Macero is an absurd planning cancer that needs to be cured.

Yes, please... lots of comprehensive studies.

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