Daylighting Intersections in Portland, OR
A site suitability analysis for prioritizing city and state funding for safer streets
To address transportation’s role in climate change, more must be done to encourage low-carbon-emitting modes of travel, namely active modes such as walking and biking. While zoning changes and parking reform can go a long way toward reducing vehicle miles traveled (VMT), the general public will only consider alternative modes like biking if they are made significantly safer through infrastructure improvements.
What is Daylighting?
Daylighting is the process of maintaining visibility of intersections and crosswalks for all users (pedestrians, cyclists and drivers) by eliminating blind spots and the resulting conflicts as users enter the intersection or crosswalk. According to Oregon state law (ORS 811.550), drivers may not park vehicles within 20 feet of a crosswalk or intersection, and Portland City Code (16.20.130) requires a distance of 50 feet in certain cases.
This StoryMap focuses heavily on biking, but bicycles are not the only type of low-carbon vehicle. Other types are important tools for working toward Portland's climate goals while also meeting commuters' transportation needs; these include, but are not limited to:
- wheelchairs
- scooters (electric or non-electric)
- skateboards
- solowheels
- mobility scooters
For the sake of simplicity, any reference to bikes, bicycles or cyclists should include all non-automobile types of mobility devices. It is important to ensure safety for all types of road user, especially those considered vulnerable.
In January 2024, I witnessed a child on a bicycle get hit by a vehicle outside an elementary school in Portland, Oregon. I attributed the cause of the crash to a lack of visibility of the intersection by a vehicle parked immediately adjacent to the ADA-compliant curb ramp (a violation under ORS 811.550). The image here shows the intersection immediately following the collision: the gray vehicle hit the child due to the vehicle in red obscuring both the child's view of the grey vehicle as it approached from the right of the frame, and the driver's view of the child as he rode into the intersection.
Paint Is Not Enough
One important caveat is that just painting a curb to inform drivers not to park near the intersection is not enough. Paint can easily be ignored, meaning the city then has to rely on expensive enforcement measures. A cleared intersection also poses a risk of drivers taking the turns faster. For this reason, New York City recently implemented a daylighting law to take effect in 2025 explicitly stating that treatments must be accompanied by physical barriers such as bollards, bike racks or planter boxes.
Daylighting in Portland, Explained
Local bike advocate Peter Kokopeli testifies before Portland City Council about the need to invest in daylighting. Oregon already has daylighting laws on the books, but violations are rarely enforced, and installations that could force compliance lack funding.
Daylighting in Hoboken, NJ
The city of Hoboken, New Jersey has had zero traffic deaths in the past seven years, due in large part to daylighting efforts at every intersection.
Daylighting Becomes Law in California
A new law in California will ban parking within 20 feet of a crosswalk starting this year, with enforcement to begin in 2025.
New Daylighting Law in NYC
A new law passed by New York City Council requires that at least 100 intersections receive daylighting treatments every year starting in 2025. This includes the important addition of physical barriers that prevent drivers from taking turns at newly cleared intersections faster.
Business owners: did you know that you can apply for a permit to place bike racks in the right-of-way in front of your business? Click the button below to learn more and submit an application!
Multi-Criteria Evaluation (MCE) using weighted linear combination (WLC)
Methodology for Selecting Daylighting Treatment Sites
To identify which Portland intersections are most in need of daylighting treatment if and when funds are procured (and how to best prioritize the funds), the following is a multi-criteria evaluation (MCE) using weighted linear combination. The aim of the criteria used in the MCE as well as how they are ranked is to determine which intersections are potentially the most dangerous for vulnerable road users (pedestrians, cyclists, wheelchair users, children, etc.) and which are most likely to be crossed frequently by those users.
A number of factors were excluded from the analysis due to the unlikelihood of pedestrians or cyclists crossing, or because they likely already lack on-street parking. Such constraints include:
- Highways and streets with posted speed limits of 40mph or higher
- Heavily industrial areas with fast-moving traffic
- Intersections of two or more high-speed arterials or collectors
- Two-way intersections
The resulting dataset was a collection of 18,143 intersections in Portland. Using these records, the analysis considered the following factors:
- Proximity to schools
- Number of ADA ramps at the intersection
- Number of streets intersecting
- Number of crashes at the intersection
- Intersects with high-speed streets
- Intersects with neighborhood greenways in commercial districts
(weightings of these factors shown in Results section)
Distance from Schools
One of the two top-ranked criteria in the analysis is distance from schools. This differs from a school zone, in that it gives a weighting system based on how close an intersection is to a school, rather than merely determining if it lies within a zone.
The analysis focuses on vulnerable road users, and one could argue that children walking and biking to school certainly fit that category. In Portland in particular, the bike bus movement is growing and Safe Routes to School programs administered by the Portland Bureau of Transportation focus heavily on encouraging active modes of transport for school-age kids.
A half-mile radius from the school was chosen, and was broken down into equal intervals of 528 feet (1/10 mile) each.
*1 indicating greatest need for daylighting treatment
Overall rank in weighted composite: 1
ADA-Compliant Ramps
The other most heavily weighted criteria is curb ramps. Because the analysis prioritizes vulnerable road users, more emphasis for safety is given to intersections where users in wheelchairs and other assisted mobility devices are most likely to cross. Mobility restrictions can often create more hazardous conditions, as a person in a wheelchair cannot as easily peek their head out to check for oncoming traffic before moving their entire body into it.
Wheelchair-accessible ramps at intersections with parked cars blocking visibility
Certain curb types were removed from the dataset, including those with bump-outs (a safety feature that prevents parking--a daylighting measure already in place) and curbs on pedestrian islands (where parking would block a travel lane). The map indicates locations with curb ramps symbolized proportionally by quantity (bigger blue circles indicate more curb ramps at that intersection).
A ranking system was used to give higher weight for intersections with the most ramps, and less weight for those with the fewest. In Portland, intersections with no ADA ramps tend to be concentrated in residential areas with less need for daylighting treatments due to their low speeds and low traffic volumes (with some exceptions), hence their low weight allocation. However, it is important to note that the low weight given to intersections without ADA-compliant curb ramps in this ranking does not indicate a lack of need for this important infrastructure; it merely reflects the low probability of people with disabilities crossing at those locations.
*1 indicating greatest need for daylighting treatment
Overall rank in weighted composite: 1
Number of Streets Intersecting
This was chosen as a higher-ranking criterion due to the complexity of four-, five- or six-way intersections and the risk they pose. In addition, the nature of a three-way intersection is such that the user approaching it from a perpendicular angle is already forced to slow down to turn.
The images here show the cross section of SE Ankeny St, Sandy Blvd and 11th Ave in Southeast Portland. This is an extremely complex intersection, with 34 total crashes between 2007 and 2021. Its complexity is exacerbated in the image below by construction work and low visibility due to the position of the sun. This is on a designated bike route and is one of the top-ranking candidates for daylighting treatment in Portland.
The ranking was broken down into five- and six-way intersections at the top, followed by four-way intersections and the lowest ranking of 5 given to three-way intersections.
*1 indicating greatest need for daylighting treatment
Overall rank in weighted composite: 2
Crash History
Crash data compiled by the Oregon Department of Transportation for the City of Portland from 2007 to 2021 was used to determine which intersections are historically the most dangerous. The data includes vulnerable road users as well as drivers, with severity levels ranging from no injury reported to fatal. However, in this analysis, fatality and injury data were not given higher weightings due to the fact that these occur more frequently on high-speed corridors and are often based on other unrelated factors, like time of day, size of vehicle, and driver impairment.
Instead, the total number of crashes at an intersection was used to determine the frequency of incidents as a measure of intersection safety and need for daylighting treatment. Because the crash count varied widely, the results were symbolized and then ranked using the Natural Breaks (Jenks) method to account for the non-uniform distribution of the data (see histogram below).
*1 indicating greatest need for daylighting treatment
Overall rank in weighted composite: 2
High Speed-Limit Streets
While streets with a speed limit of 40 mph or higher were excluded from the analysis (due to the unlikelihood of pedestrians/cyclists crossing and lack of on-street parking), speed was an important factor in determining where daylighting is needed. According to the National Association of City Transportation Officials (NACTO) , speed is the deadliest factor in whether a crash is fatal, particularly for vulnerable road users.
As shown above, a collision with a pedestrian at just 30 mph has a roughly 90% chance of causing serious injury and greater than 50% chance of causing death. Even the relatively slow speed of 25 mph is fatal for the pedestrian 1/4 of the time.
The ranking therefore gives the highest weight to faster zones within school zones, followed by those outside of school zones (slide map to see zones). The lowest weight is given to streets with slow speeds of 20 mph or less.
*1 indicating greatest need for daylighting treatment
Overall rank in weighted composite: 3
Bike Routes in Commercial Zones
This criterion was suggested by a PBOT employee, whose expertise indicated potential conflicts from drivers circling to look for parking in commercial areas containing or adjacent to neighborhood greenways. The City of Portland designates neighborhood greenways as priority routes for those traveling by bike, and these sometimes run through areas with heavy retail activity (particularly in Northwest Portland). The mixture of circling traffic at businesses and high numbers of cyclists present a conflict. However, this is the lowest ranked criterion in the overall weighting due to the low speeds and heavy presence of diverters on neighborhood greenways, making potential crashes less severe.
*1 indicating greatest need for daylighting treatment
Overall rank in weighted composite: 3
Final Analysis: Importance Weight
In performing the analysis, the above criteria were ranked and given the weights below based on relative importance. The numerator was then calculated and divided by the total sum of numerators to determine the final weight.
These weights were then calculated in ArcGIS and a ranking of 1-5 was obtained for the roughly 18k intersections in Portland.
Results
The analysis did not yield any results with a rank of 1, so the results for the rank of 2 were used instead. This rank produced a total of 120 results, shown in the map below on the left. The rank of 3 produced 4,055 results, shown below on the right.
In 2022, the City of Portland spent $200,000 daylighting 350 intersections , at an average cost of $571 each. At that rate, funding for the top-ranked intersections in this analysis would come out to just under $70k, and daylighting the next-highest ranked intersections would cost roughly $2.3 million.
Limitations
My original analysis had called for excluding all streets from the data where parking is prohibited entirely, or where the street only has travel lanes. This would eliminate areas that do not need daylighting treatments by their nature. Unfortunately, according to an employee of the Portland Bureau of Transportation, the city does not collect this data and only has datasets for no-parking signs. I found this data to be extremely unreliable, as a check for certain sign codes in the spatial data were incorrect when I checked them against Google Maps images (e.g., "No parking this block" found on Google Maps in a location the city's data showed as having the map code for "No parking this block 8AM-5PM MON-FRI.").
Moreover, some of the streets adjacent to intersections in the data may already have certain daylighting treatments or other elements that improve visibility by preventing on-street parking close to intersections. These may include, for example, on-street bike racks, fire hydrants or bus stops.
As a result, this analysis should serve only as a starting point. The suitability of the intersections analyzed here can ultimately only be determined after visual inspection of the ranked site, which can initially be done by a Google Map image search, but ultimately should involve an in-person visit prior to committing to changes. This will also help determine which streets adjacent to the intersection need treatment and rule out any that have not already been updated by the city since the data used in this analysis was published.
Other Potential Future Analyses
Other analyses can be performed in the future to determine suitable sites for daylighting treatments depending on the issuance of grants and interest of private businesses. These include:
- Targeting businesses that may want to apply for on-street bike racks
- Neighborhood greenways proximate to commercial areas
- Bars (to discourage drinking and driving)
- Commercial districts
- Narrowing down by neighborhoods (for neighborhood associations to apply for ODOT grants)
- High crash intersections/streets (if parking is legal on those streets)
- Streets which intersect with high speed streets (25 mph or higher)
- Near schools, all adjacent intersections
- History of crashes
