In a correction notice dated January 4, 2016, Seattle DPD asked the developer for proposed project 417 NE 73rd St to conduct a study to measure on-street parking demand in the surrounding neighborhood:
Please conduct an on-street parking utilization study, generally following the guidelines for such studies as described in TIP 117. On-street spaces within 800′ of the project site should be included in the study area. Impacts should be documented during both the time period of peak residential parking demand, and the time period of peak parking demand generated by Rosita’s restaurant.
The request, no doubt, was prompted by the barrage of complaints that the community had made in meetings and online asking why a 45 unit apartment complex with parking for 13 subcompact cars was being built in a neighborhood where on-street parking already regularly exceeds legal capacity, especially during nice weather.
The developer wasted little time in producing a response. Barely two weeks after DPD made its request, on the nights of January 20 and 21, a transportation engineering firm was scurrying up and down the streets in the east Green Lake community taking measurements and counting cars. Just three weeks after that the numbers had been crunched and Seattle DPD posted the report online for review.
Presumably, they also read it.
However, before we get to that, we want to provide an overview of the basics of parking utilization studies.
The goal of these studies is to give a reasonable estimate of how much legal street parking capacity drivers use in an area, especially during peak periods. TIP 117 outlines a step-by-step process on how to go about this:
Define the study area. For 417, the study area consisted of all blocks within 800 feet walking distance (i.e., measured along streets) of the project site.
Determine the sections of a block where parking is legal. If a street side has a 20 foot wide driveway, a fire hydrant, and stop signs on both ends, for example, 30 feet would be removed for each stop sign, 30 feet would be removed for the driveway (20 feet plus 5 feet of clearance on either side), and 30 feet would be removed for the hydrant (15 feet on either side). The street sections that remain are where parking is legal.
Determine the legal parking capacity. For each street section where parking is legal, determine its parking capacity. Using TIP 117 guidelines, a section that is 16 to 31 feet in length will accommodate 1 car, one that is 70-91 feet will accommodate 4, and a section that is 260-281 feet in length will accommodate 14 cars, for example.
Count parked cars. On at least two different days, during peak demand, count the number of cars parked on each block face in the study area. According to TIP 117, this count should take place during the middle of the week and in the evening.
With this data organized, the parking utilization for a street side can be calculated. If a block face has two segments where parking is legal, one 150 feet in length, the other 250 feet, for example, then according to the TIP 117 guidelines 21 cars can legally park on that side. If the number of cars observed parked there is 16 on one night and 13 the next, then the parking utilization for the block face is 14.5/21 = 69% (i.e., the average of the number of parked cars divided by the legal street capacity on the block face).
As should be apparent from the description above, a parking utilization study is only as good as its data collection.
So how did the study conducted for 417 fare?
Not so well based on our review. Every street we looked at in the study area—and we only sampled a handful—contained errors. The details including photos appear below and a summary map can be found here.
NE 73rd St
- On the northwest corner of NE 73rd St and 5th Ave NE, the study claims that 20 feet of legal street parking exists, enough for one car. We found no legal parking on this corner. This would have been true even without the fire hydrant, which the study missed.
- On the southwest corner of NE 73rd St and 5th Ave NE, the study claims that 36 feet of legal parking exists, enough for two cars. We found only 11 feet, not enough for even a single car.
- On the southwest segment between 5th Ave NE and Woodlawn Ave NE, the study claims that 81 feet of legal parking exists, enough for four cars. We found 58 feet, barely enough for three cars.
- The study collected parking data only once for the south side of the street, not nearly enough for reliable parking utilization estimates. TIP 117 sampling guidelines clearly state that parked cars should be counted on at least two different days.
Based on our measurements, the study’s estimated legal street parking capacity on NE 73rd between 5th Ave NE and Woodlawn Ave NE was four cars greater than what it should have been. Using these measurements and the parking data the study did collect, this street section was at 110 percent of legal parking capacity during the periods when cars were counted.
NE Maple Leaf Pl
- On the north side of NE Maple Leaf Pl, the study missed a fire hydrant, inflating the legal parking capacity on that side by 30 feet.
4th Ave NE
- More than 450 feet of 4th Ave NE north of Woodlawn Ave NE was omitted from the analysis, even though it fell within in the study zone stipulated by Seattle DPD.1
- Not that it mattered. The study did not collect parking data for 4th Ave NE, and it provided no parking utilization rates for the nearly 1400 foot of portion of the street residing in the study zone.This omission violated Seattle DPD instructions.
Woodlawn Ave NE
- On the east side of Woodlawn Ave NE, between NE Maple Leaf Pl and NE 72nd St, the study missed an alley, inflating the legal parking capacity for this side of the block by 34 feet.
- The study collected parking data only once for the 1600 feet of Woodlawn between NE Maple Leaf Pl and NE Ravenna Blvd, not nearly enough for reliable utilization estimates. TIP 117 sampling guidelines clearly state that parked cars should be counted on at least two different days.
NE 71st St
- 419 NE 71st St, a project currently under construction, falls within the study zone for the 417 parking utilization study. Because of this, spillover parking from 419 should have been included as part of a cumulative parking study DPD requested from the developer in a January 4, 2016 correction notice for 417. It was not.
The study also provided an inexplicable summary statement:
Based on the data collected and completing the “Block Front Plan Data Sheet” for all applicable blocks, what was found was Day 1 to be at 106 percent of measured capacity and Day 2 to be 102 percent of measured capacity.
Since the study collected insufficient or no parking data for significant portions of the study zone—3500 feet according to our estimates—block data sheets clearly were not completed “for all applicable blocks” despite the claim. Also, TIP 117 only provides guidelines on how to calculate parking utilization rates for each block face in a study area, and the study doesn’t explain how it calculated rates for the entire study zone.
Inflated parking capacity, missing alleys and other critical street features, unreliable or missing statistics, mislabeled streets. Seattle DPD would certainly be aware of these serious issues if they checked the study—a study they requested in the first place. However, as we’ve discussed here and here, DPD has been supine when it comes to reviewing traffic studies in the east Green Lake community, and it’s not clear why this time will be any different.
1 All distances are for each side of a street.