tc431 (4).pdf
PDF 350 KB Posted
- Solicitation number
- 645-RFB-2407-2026
- Issued by
- Johnson County, Iowa
About this file
This is a Standard Road Plan document (TC-431) issued by the Iowa Department of Transportation (Iowa DOT) that provides traffic control specifications for left and right lane closures during maintenance operations. The document establishes standardized configurations for managing traffic flow around work zones, detailing the placement and spacing of shadow vehicles, protection vehicles, truck-mounted attenuators (TMAs), arrow boards, and warning signs for operations conducted at various speed limits. The plan addresses two primary scenarios: operations on roadways with speed limits of 55 mph or greater, and operations on roadways with speed limits of 50 mph or less. For each scenario, the document specifies roll-ahead distances, vehicle spacing requirements, and sign placement requirements based on vehicle gross vehicle weight ratings (GVWRs) ranging from 9,900 to over 22,000 pounds. The plan requires all vehicles to be equipped with amber revolving or strobe lights, mandates fluorescent yellow-green (FYG) sign backgrounds for all static signs, and recommends TMAs for speed limits of 30 mph or more. The document was revised on 04-15-25 with interim provisions removed and approved by the Design Methods Engineer.
The traffic control plan establishes operational requirements for Iowa DOT maintenance crews to keep work areas as small as possible while safely accommodating the work being performed. Shadow vehicles 1, 2, and 3 will utilize dump trucks or heavy-duty vehicles and may encroach into the travel lane when shoulder width and strength do not permit safe shoulder operation. Shadow Vehicle 4 positioning may be adjusted to create a taper when conditions allow. The plan requires an Audible Warning System for certain operations, with specific timing criteria detailed in Appendix A, and recommends such systems for Iowa DOT maintenance operations. The document references additional traffic control plans (TC-415, TC-418, and TC-419) for operations not meeting the minimum 500-feet-per-30-minute movement criteria, and provides links to the Iowa DOT Design Manual and Appendix A for supplementary guidance on implementation and specific operational requirements.
View the file
Other files
On GovTribe
Work with this file
- Download the original file
- Contacts named in this file
- Similar government files
- Ask GovTribe AI about this file
Text version
LEFT LANE CLOSURE
Traffic Control
Possibe Contract Item:
doing so would negatively impact the work being performed.
Adjust the lateral position of Shadow Vehicle 4 to create a taper unless when shoulder width and strength allow.
will use dump trucks/heavy duty vehicles for shadow vehicles 1, 2, and 3 shoulder is too narrow to drive on. Iowa DOT maintenance operations
Shadow vehicles 1, 2, and 3 may encroach into the travel lane when the appendix A for times when an Audible Warning System is required.
Audible Warning System recommended. Iowa DOT maintenance crews see place.
Keep work area as small as possible to safely accommodate the work taking
TC-431
REVISION
04-15-25
SHEET 1 of 2
REVISIONS: Removed interim.
APPROVED BY DESIGN METHODS ENGINEER
STANDARD ROAD PLAN
OPERATING IN THE TRAFFIC LANE
SLOW MOVING VEHICLE
R
500' R
LEGEND
Work Area
Direction of Traffic
(TMA)
Truck-Mounted Attenuator
Arrow Board
RIGHT LANE CLOSURE
500'
Shadow Vehicle 2
Shadow Vehicle 4 Protection Vehicle 1
Protection Vehicle 1Shadow Vehicle 4
(optional)
Shadow Vehicle 3 Shadow Vehicle 2
500' 500'
Work Area
Work Area
55 MPH OR GREATER
48" x 48"
W20-1
ROAD
WORK
AHEAD
48" x 48"
W20-1
ROAD
WORK
AHEAD
Maintenance Appendix A
500'
500' criteria, use TC-415, TC-418, or TC-419.
within every 30-minute timeframe. For operations not meeting this
This layout is intended for use with operations moving at least 500 feet static signs.
Fluorescent yellow green (FYG) sign background is required around all
Equip all vehicles with an amber revolving light or amber strobe light.
43 3
(optional)
Shadow Vehicle 3
48" x 48"
W20-5
CLOSED
AHEAD
LEFT LANE
48" x 48"
W20-5
RIGHT LANE
CLOSED
AHEAD
500'
500'
(optional)
Shadow Vehicle 1
(optional)
Shadow Vehicle 1
200' 240'
Roll Ahead Distance (R)
9900 to 22,000 lbs. GVW Over 22,000 lbs. GVW
Stationary 15 mph Max
Moving Stationary
15 mph Max
Moving
160' 200'
48" x 48"
W20-5
RIGHT LANE
CLOSED
AHEAD
Or
48" x 48"
W20-5
CLOSED
AHEAD
LEFT LANE
Or
DOT
https://www.iowadot.gov/design/dmanual/01e-06.pdf https://iowadot.gov/dotnet/Maintenance/Docs/AppendixAApproved.pdf
LEFT LANE CLOSURE
TMA recommended for speed limits of 30 mph or more.
vehicles 1 and 2 when shoulder width and strength allow.
operations will use dump trucks/heavy duty vehicles for shadow shoulder is too narrow to drive on. Iowa DOT maintenance
Shadow vehicles 1 and 2 may encroach into the travel lane when the
System is required.
crews, see Appendix A for times when an Audible Warning
Audible Warning System recommended. Iowa DOT Maintenance taking place.
Keep work area as small as possible to safely accommodate the work
TC-431
REVISION
04-15-25
SHEET 2 of 2
REVISIONS: Removed interim.
APPROVED BY DESIGN METHODS ENGINEER
STANDARD ROAD PLAN
OPERATING IN THE TRAFFIC LANE
SLOW MOVING VEHICLE
R
48" x 48"
W20-5
RIGHT LANE
CLOSED
AHEAD
A
R
48" x 48"
W20-5
CLOSED
AHEAD
LEFT LANE
100' 100'25-40
Roll Ahead Distance (R)
9900 to 22,000 lbs. GVW Over 22,000 lbs. GVW
Stationary 15 mph Max
Moving Stationary
15 mph Max
Moving
75' 100'500'
Spacing
Vehicle
125' 175'45 100' 150'
750'
1500'
A
200' 240' 160' 200'
LEGEND
Work Area
Direction of Traffic
(TMA)
Truck-Mounted Attenuator
Arrow Board
RIGHT LANE CLOSURE
* Speed Limit refers to regulatory speed limit before road work.
(mph)*
LIMIT
SPEED
Shadow Vehicle 1
Protection Vehicle 1
3 2 5
Protection Vehicle 1
Shadow Vehicle 1
A
50 MPH OR LESS
Work Area
Work Area use TC-415, TC-418, or TC-419.
within every 30-minute timeframe. For operations not meeting this criteria, This layout is intended for use with operations moving at least 500 feet static signs.
Fluorescent yellow green (FYG) sign background is required around all
Equip all vehicles with an amber revolving light or amber strobe light.
3 2 5
DOT
| tc431 |
| tc431 |
File details come from the government source that posted it. Updated .