Seattle traffic control plan requirements
SDOT Client Assistance Memo 2111 is the submittal checklist. The City of Seattle Traffic Control Manual for In-Street Work explains how Seattle interprets the federal MUTCD, and governs where the two differ.
Published requirements
Transcribed from Seattle's own published document. Each entry cites where it came from and when it was last checked.
If only one lane is open in a direction, that lane shall be a minimum of 11 feet wide. Each lane must be at least 11 feet wide when only one lane is available in one direction.
11 ftSeattle SDOT CAM 2111, Standard Note 6 and "Revised traffic lane widths" · Verified 2026-08-21
Where spotters or flaggers are used, the single open lane may be a minimum of 10 feet wide.
10 ftSeattle SDOT CAM 2111, Standard Note 6 · Verified 2026-08-21
A sidewalk is closed if a minimum 4-foot path cannot be maintained measured from the property line.
4 ftSeattle SDOT CAM 2111, Standard Note 4 · Verified 2026-08-21
Where the pedestrian path is created from the face of curb rather than the property line, the minimum is 5½ feet.
5.5 ftSeattle SDOT CAM 2111, Standard Note 4 · Verified 2026-08-21
Include a scale bar if feasible. Preferred scales are 1:20, 1:30, 1:40, 1:50 and 1:60.
Seattle SDOT CAM 2111, Title Block Requirements · Verified 2026-08-21
Five working days notice to King County Metro Transit for any work requiring a temporary bus stop. Ten working days to relocate a bus shelter or reroute service; fifteen to deactivate overhead trolley wires. No two consecutive transit stops may be closed.
5 daysSeattle SDOT CAM 2111, section 4 Coordination Requirements · Verified 2026-08-21
Ten business days notice for haul route approval and for long-term parking impacts or pay station removal. Bike lane and trail closures require 72 hours public notice via on-site signage.
10 daysSeattle SDOT CAM 2111, section 4 Coordination Requirements · Verified 2026-08-21
Traffic Control Plans are submitted as part of a Street Use permit application package, by email to SDOTPermits@seattle.gov, or SDOTUtilPermits@seattle.gov for utility permits.
Seattle SDOT CAM 2111, section 5 How to Submit a TCP · Verified 2026-08-21
Source
https://www.seattle.gov/Documents/Departments/SDOT/CAMs/cam2111.pdfDocument revision date: 2017-12-05
Agencies revise these documents without notice. If something here is out of date, tell us at hello@conemap.com and it will be corrected. Report a discrepancy.
Taper length for a Seattle work zone
Taper geometry is federal — it comes from MUTCD 11th Edition Tables 6B-3 and 6B-4 wherever you are. What Seattle adds is the checklist above.
Posted speed limit, off-peak 85th-percentile speed prior to work starting, or anticipated operating speed.
How far traffic is moved sideways — usually the width of the closed lane.
Merging taper length
245ft
L = W × S² ÷ 60 = 12 × 35² ÷ 60 = 245.0 ft
MUTCD 11th Ed, Tables 6B-3 and 6B-4 — at least L
Plan view
8 devices at 35 ftLength is to scale; the lateral offset is exaggerated so the taper is legible.
All taper types at these conditions
MUTCD 11th Ed, Table 6B-3Merging taper
at least L
245 ft
Shifting taper
at least 0.5 L
125 ft
Shoulder taper
at least 0.33 L
85 ft
One-lane, two-way traffic taper
50 ft min, 100 ft max
50 ft
Downstream taper
50 ft min, 100 ft max
50 ft
Channelizing devices
MUTCD 11th Ed, Section 6K.01Maximum spacing in this taper
1 × 35 mph
35 ft
Devices required
One at each end, evenly spaced between
8