08/04/2025
Hello everyone!
The second most often asked question I get while campaigning is about the effect of the Town Center on traffic and congestion.
As I’ve stated on my website, flyer and postings, I believe that the traffic analysis performed for the SEIS regarding the Town Center is insufficient and deeply flawed in its methodology. The city utilizes a program called Syncho 12. The analytical approach is static and deterministic when it should be dynamic and probabilistic. It does not analyze traffic as a connected system but instead studies intersections in isolation. Traffic impact is typically grossly understated when using a static / deterministic and non-systems approach as this methodology does not consider time, variation and the interaction between variables. The TMP notes limitation examples such as “not accounting for queuing and delay impacts which occur when intersection operations are interrupted by queuing from a downstream intersection… or modeling unserved demand, which occurs when an intersection operates with oversaturated conditions for an extended period of time”. I believe that the predicted traffic behavior from the SEIS analysis shows a much greater positive traffic condition than what will result in the real world after construction.
But to contrast the academic or theoretical with some common sense, consider the following. From the NHSTA (2021) data, cars per dwelling type are Single Family at 2.1, Townhomes at 1.8, Duplex at 1.6 and Apartments at 1.1. If we assume the proportion of those dwelling types in Town Center for Single Family, Townhomes, Duplex and Apartments are 5%, 20%, 30% and 45% respectively, we can use a weighted average to determine a car count of 2880 for 2000 dwellings and 5760 for 4000 dwellings. From the NHSTA, households average roughly 5 trips per day such that we would see 14,400 trips from 2000 dwellings and 28,800 trips for 4000 dwellings.
To put this into perspective, our TMP shows the current vehicle volume of 20,188 at the intersection of 228th and 4th (i.e. Met Market). A portion of the 14,400 trips (2000 dwellings) or 28,800 trips (4000 dwellings) will utilize this intersection. If we consider the proposed volume of commercial activity in Town Center, the vehicle volume increases to 18,130 trips for 2000 dwellings and 32,530 trips per day for 4000 dwellings (current retail of 134,000 sq ft at 1000 trips per day, and future retail of 366,000 sq ft at 2730 trips per day).
Therefore, the intersection of 228th and 4th would see 1.89X increase in volume (20,188 to 38,318) for 2000 dwelling units or a 2.61X (20,188 to 52,718) increase in volume for 4000 dwellings over the current conditions. It is difficult to believe that transit solutions will alleviate this increase. If a typical city bus carries 80 passengers when full, we would need 227 bus trips (2000 dwellings) or 407 bus trips (4000 dwellings) to maintain the current state. Although my wife says that this is too much math, the impact of Town Center on traffic is not insignificant, it is extremely consequential.
Michael Boyer for Sammamish City Council “I’ve proudly called Sammamish home for 30 years. My wife and I raised our two sons here and wish to stay. Now retired and on a fixed income, that desire has become a difficult proposition. I am running for City Council to ensure that all residents, regar...
