Transportation Design Standards Update

Topic

Generally, staff were asked to consider weather conditions and to make sure transit vehicles were accommodated. There were several items that were brought to staff’s attention that resulted in changes to this section. As suggested by community members, a figure was added to Ch. 2 to describe the features of a Right Turn Raised Crossing. Staff have also updated bus lanes widths from 12' wide to 11' wide based on comments from community members. Concerns about double left-hand turn lanes were also raised. In response, staff added language for Director approval on double lefts.

There were also requests for a “maximum” turning radius. Staff determined that creating a blanket "maximum" turning radius would make off-set intersections require additional ROW to construct. However, per Ch. 2 the smallest feasible flowline curb radii should be selected for corner designs.

Comments question the need for standard and buffered bike facilities. Bike lane facility types were determined in the City’s Low-Stress Walk and Bike Network Study previously, and changes to these designations are outside the scope of this DCS Update. There are physically constrained streets where there is only space for a conventional bike lane so having a facility in the DCS with parameters for their design and construction will support consistent and more effective outcomes when this facility is developed.

Clarification was provided on the difference between traffic circles and roundabouts, specifically, circles do not move curb ramp locations and benefit pedestrians by providing safer crossings with lower vehicle speeds. The team also added guidance on transit operations around traffic circles.

There were questions about shifting lanes and tapers, which are based on a formula from the Manual of Uniform Traffic Control Devices and on the slower operating speed of a bicycle. There were also general concerns about separate bike lanes treatments, intersection treatments, contra-flow lanes, and excessive marking and signing.

Some comments, such as those regarding chicanes, truck aprons, and bicycle wayfinding signage, could be included in a future project phase. Other comments, like education, enforcement, and speed setting, are outside the scope of this project.

Comments received request standards for rain gardens. Requirements for the design and construction of rain gardens and other stormwater facilities are covered in BRC 11-5 and DCS Chapter 7.

Comments also encouraged the use of native species in project landscaping, and enabling language has been added to reference resources such as the City’s Revegetation Best Management Practices guidebook, which includes native species.

No or minimal comments were received.

No or minimal comments were received.

Update lane widths table with new, narrower preferred widths to align with current best practice for constructing streets that serve people walking and bicycling. See Table 2.5

Anticipated benefit: Narrower lane widths typically yield slower vehicle speeds

Add lane widths for all expected types of bike lanes including conventional, buffered, separated, and parking-protected. See Table 2.5

Anticipated benefit: Providing standard widths for bicycle lanes will lead to more consistent projects that prioritize bicyclist safety and comfort

Provide additional technical information about operating speed of bicyclists and the effect on design features

Anticipated benefit: Providing more nuanced information about separated bike lane design will lead to more consistent design of separated bike lanes that are comfortable for bicyclists of all ages and abilities

Update guidance and standards to help designers achieve smaller effective radii of curbs, especially through the use of curb extensions. See 2.07 (D)(5)(d) Figures 1 and 2

Anticipated benefit: Slower turning speeds and increased comfort for people walking and biking

Add information about bike lane tapers in addition to existing motor vehicle lane tapers

Anticipated benefit: Eliminating bike lane designs with abrupt tapers (changes in direction) that can cause rider discomfort

Clarify goal to use a single left-turn lane first, then dual left turns if necessary. Add statement that triple left-turn lanes are only allowed with Director approval.

Anticipated benefit: Reducing the number of left-turn lanes at intersections shortens crossing distances for pedestrians and bicyclists

Add new figures

Anticipated benefit: Separated bike lanes typically cross driveways and alleys. Standardizing this element of design can improve visibility of bicyclists and improve yielding compliance.

Add new figures

Anticipated benefit: The most complex aspect of separated bike lanes is at intersections. Providing examples of how to maintain safety and good sightlines through the intersection will lead to consistent design of future projects.

Add new figures

Anticipated benefit: Neighborhood traffic circles are a great traffic calming technique for local streets. Standardizing their design with typical dimensions will help provide consistent design of future projects.

Add new figure

Anticipated benefit: Standardizing raised crossing design will help provide consistent traffic calming and yielding compliance benefits.

Add new drawing

Anticipated benefit: Provide a detailed standard for bike ramps that connect on-street bike lanes to sidewalk-level multi-use paths, providing a more comfortable and safe transition for bicyclists of all ages and abilities

Add new drawing

Anticipated benefit: Curb extensions help slow turning vehicles and reduce pedestrian and bicyclist crossing distances. A new standard drawing will lead to consistent design of future projects.

Add new drawing

Anticipated benefit: Many streets proposed for separated bike lanes also have bus routes. A new standard drawing will lead to consistent design of future projects.

Add new drawing

Anticipated benefit: Raised crossings slow vehicles and make pedestrians more visible. A new standard drawing will lead to consistent design of future projects.

Update drawing

Anticipated benefit: Noted maximum vertical clearance of 8' to match Ch. 2 text.

Update drawing

Anticipated benefit: Changed minimum intersection radius from 10' to 5' to match Ch. 2 figure.

Update drawing

Anticipated benefit: Added 4' min width for a landscaped median; added a note for 4" min depth of topsoil required to match Ch. 3 text

Update drawing

Anticipated benefit: Changed minimum separated bike lane width to 6.5' min, 7' preferred to match Ch. 2 text.

Update drawing

Anticipated benefit: Changed vertical clearance to 8' to match Ch. 2 text; changed max foreslope/backslope from 4:1 to 3:1; changed shoulders to earth pattern, removed on-street bike lane typical section.

Update two drawings: Arterials and Collectors

Anticipated benefit: Added note for designer to verify if route is on Boulder's Low Stress Walk and Bike Network, which has implications for recommended facility type between on-street bike lanes and separated bike lanes.

Update standard drawing to include more details about tree spacing in different streetscape contexts

Anticipated benefit: Will lead to consistency in planting locations

Add a secondary standard drawing that shows the offset distances for various amenities and utilities

Anticipated benefit: Makes the offset requirements more clear visually, aiding designers in developing great landscape plans.

Update drawing to include tree guard and revised tree grate detail. Modify location of amended soil. Add information on soil volume.

Anticipated benefit: Provide a standard for tree plantings in urban sidewalk areas that will lead to a healthier tree thereby increasing tree canopy.

Remove tree species references in standards text and insert reference to regularly updated tree list

Anticipated benefit: Allows Boulder Forestry staff to maintain an Approved Tree List that can be updated on a regular basis to provide the best trees for the local context at any given time.

Update Tree Species table with more modern standards. Updated table

Anticipated benefit: Promote tree diversity in the City of Boulder and reduce instances of monoculture plantings of trees.

Increase minimum soil volumes

Anticipated benefit: Promote healthier trees

Update standard drawing to include more details about tree spacing in different streetscape contexts. Updated drawing

Anticipated benefit: Will lead to consistency in planting locations

Add a secondary standard drawing that shows the offset distances for various amenities and utilities. New drawing

Anticipated benefit: Makes the offset requirements more clear visually, aiding designers in developing great landscape plans

Updated drawing to include tree guard and revised tree grate detail. Modify location of amended soil. Add information on soil volume.

Anticipated benefit: Provide a standard for tree plantings in urban sidewalk areas that will lead to a healthier tree thereby increasing tree canopy.

Updated soil definitions to match modern standards

Anticipated benefit: Improvement in quality of soil and clarity on soil amendments.

This is not a new sight triangle. The proposed change will change the location of where the sides of the sight triangle are measured when the public street has a sidewalk. Currently the sight triangle is measured along the right-of-way line of the public street and either the right-of-way line of the public alley or the edge of the private driveway and whose third side is a line connecting the two sides. Updated figure

Anticipated benefit: This change will provide staff with physical features to measure the sides of the sight triangle when responding to sight triangle complaints.

This is a new 15’ x 96’ sight triangle that will be added to the sight triangle section of the Boulder Revised Code. The sides of the new multi-use path sight triangle would be 15’ x 96’ with the third side of the sight triangle being the line that connects the two sides. New figure

Anticipated benefit: The 15’ x 15’ sight triangle is currently used where a multi-use path (path) intersects with either a driveway or alley. The new sight triangle increases the sight triangle area between the path and either a driveway or alley.