Comparing the alternatives

Options A and B create more safety for everyone and improve routine emergency access compared to C and D. C and D are much more expensive and slower to implement because utilities must be moved, curb & gutter work, additional concrete, and additional right-of-way purchased.. In a disaster situation when people want to drive eastward, the two-way bike path of B and D provide a contra-flow lane for emergency vehicles traveling west.  

Community Cycles built a comparison table based on that information and our knowledge of bicycling infrastructure.See our comparison table.


Safety comes first, right? Not today on Iris Ave. All four alternatives will improve safety because they all add protected bicycle lanes. But rebalancing into a 4-to-3 configuration definitely improves safety compared to a regular four-lane road and the biggest beneficiaries may be car drivers, who will be less likely to get rear-ended or broad-sided while making a left turn.

Crossing the street is safer in the 3-lane configuration because pedestrians and cyclists have shorter distances across conflicting car movements and because visibility is better. With four lanes, mid-block signalized crosswalks have the problem that car drivers in one lane may stop, but they can block visibility of the person crossing to drivers in the other lane.

Expense & Time to Completion

Boulder has had recent experience with roadway redesigns of the kind envisioned in options A & B. With no need to expand the right of way and relocate utilities, projects like this might be expected to cost about $5 million dollars (based on the Baseline project) and could be completed in two or three years.

By contrast, options C & D would require demolishing the existing curbs and building new ones further out, plus additional, new pavement. The existing right-of-way is not wide enough for C&D, so these options would require the purchase or condemnation of private property along Iris. Into this expanded right of way, the City would then need to move major utilities including street lights, water, sewer, and electrical. The widening would require removal of many mature trees.

When roadways have been completely re-engineered in this way, it usually costs about 3 or 4 times as much as a road rebalancing, so we expect that options C and D would cost some $20 million dollars or more. The project would take roughly 20 years. Thus, options C and D are tantamount to no action to improve the safety of Iris for more than a decade.


The slower vehicle speeds expected with options A or B should reduce road noise by 5 to 6 decibels. That may not sound like a lot but it’s important to remember that the decibel scale is logarithmic, so this reduction in road noise would be difference between shouting to be heard over passing traffic to being able to comfortably converse in normal voice, whether you are walking or rolling down Iris or sitting in an abutting yard.


If a significant number of mature trees would need to be removed for options C or D, then options A & B would have the benefit of preserving those trees with the expectation that they would continue to offer shade to pedestrians that travel along Iris (as well as the yards of abutting residences).

Access to Protected Bikelanes

For cyclists approaching Iris from the South, options B & D create a  need to cross Iris in order to access the bi-directional cycle track located on the North side. This disadvantage can be mitigated with  protected intersections elements, which make pedestrian and bicyclist movement through intersections much more safe. Options A and B have sufficient room for robust protected intersections.


One conspicuous benefit of options B and D is that a cycle track on the North side of Iris will receive better exposure to the sun, allowing snow to melt more quickly and making it less likely that ice that has formed on cold evenings will persist over the course of the day.


People are reasonably concerned about how the changes to Iris will affect us in emergencies. Here is what we glean from the options and the feedback from the response from Boulder’s Office of Disaster Management.

Routine Emergency Service Vehicle Access

For day-to-day emergencies, the kind that occur routinely and require fast movement of fire trucks, ambulances, or police, the City’s presentation of the alternatives assigns a + symbol to alternatives A and B, while assigning a – symbol to alternatives C and D. The reason for this is the center turning lane in the three-lane configuration. On a four-lane road, emergency responders must weave around cars that may be blocking all four lanes. Drivers must move to the side and that can cause delay and even crashes. With a center turning lane, it will generally be clear and available for the emergency vehicles. Also, the widening in alternatives C and D will use up the three-foot margins that now serve as bike lanes. So cars will have less room to pull over for emergency vehicles. To summarize, the rebalancing options improve routine emergency responses, while the alternatives that maintain four lanes slightly worsens emergency vehicle travel.

Evacuation & Disaster Response

The Marshall Fire made us all aware of how vulnerable Boulder is to wildfire. What would happen if wildfire invaded the west side of the north half of the city? Would the reconfiguration of Iris mean that people cannot evacuate fast enough, or that emergency responders could not get to the fire? 

For the category of “Disaster emergency response”, the City documents assign a negative sign to Alternative A, the road rebalancing with bike lanes on both sides, because it would constrain the road more than its current configuration. But for Alternative B, the road rebalancing with a two-way cycle track on the north side of Iris, the City assigns a positive symbol because that cycle track would be wide enough for fire trucks and ambulances to travel westward, free of oncoming cars. 

For the two options that would maintain a four-lane configuration, the City assigns a neutral score for disaster response under Alternative C, the version that has bike lanes on both sides. For emergency vehicles it would act much like Iris currently does. For Alternative D, the City assigns a positive score for the same reason it gives a positive to Alternative B: Emergency vehicles could use the two-way bike lane for westbound travel.  The city’s fire, ambulance, and police departments have endorsed both alternatives B and D.

Note that eastbound public travel during an evacuation would not occur only on Iris. People would also use Violet, Norwood, Kalmia, Hawthorne, Grape, and Glenwood, and Balsam-Edgewood streets.



Report a Maintenance Problem, City of Boulder

City of Boulder: To report a street maintenance related problem (potholes on the bike path, paths blocked by snow), complete the form and provide your contact information.


Report County Road Service Issue

Boulder County: To report a street maintenance related problem (potholes on the bike path, paths blocked by snow), complete the form and provide your contact information.


Report an Aggressive Driver

If you find yourself in a situation with an aggressive driver, remember you can dial *CSP (*277), free of charge. Report “real time” aggressive driving behavior to the Colorado State Patrol.


Report a Close Call – Inquire Boulder

Have you had a close call with a bicycle, pedestrian or motorist? This data is important and used in analysis of the safety of our streets.


Bike Theft Prevention & Registration

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