11E-1: Speed Limit Increase Implementation Plan

This guidance is provided to support decision making for highway improvement projects that are under development as of July 1, 2026, when the posted speed limit change enacted under Senate File 378 took effect. The statutory change increases the default speed limit to 60 mph on any roadway where the posted limit was not established through an engineering and traffic investigation. This change will primarily affect rural two-lane highways, with additional impacts on certain four lane divided and urban segments.

Guidance

This guidance is for projects currently being developed with a 60-mph design speed.

• Projects that are in the pre-D2 (field exam event) development stage as of July 1, 2026, will, in nearly all cases, be changed to a 65-mph design speed.
• Projects that are in development past the D2 event as of July 1, 2026, will remain as designed and without modification based on the speed limit change.

Notes

• The speed limit change does not apply to the interstate system
• The speed limit change establishes a statewide framework for implementation and does not mandate a uniform application across the entire system. Lower posted speeds may still be applied where supported by engineering and traffic studies.
• Future project development will strive to achieve a 65‑mph design speed on the majority of eligible system segments. However, this guidance does not preclude the use of design flexibility on limited portions of the system where balancing roadway user needs and site constraints results in a posted speed limit below 60 mph.
• Design decisions shall reflect the intent of the statute, which is to provide 60‑mph roadways wherever appropriate. Designers should avoid choices that unnecessarily constrain a segment to a lower posted speed when a higher compliant speed is reasonably achievable.
• System consistency and operations for drivers will be a high priority.
• District engineering judgement will guide project-level decisions.
• All Iowa DOT highway design methodologies shall remain harmonized with the currently adopted version of the American Association of State Highway and Transportation Officials publication, “A Policy on Geometric Design of Highways and Streets.” This approach reflects current Iowa DOT practice and will remain unchanged following enactment of the statute.
• The methodology for bridge replacement projects will remain unchanged regarding horizontal and/or vertical geometry to achieve the 65-mph design speed. The current Iowa Crash Analysis Tool (ICAT) based benefit cost evaluations method still applies: if accident history, overtopping history, and roadway performance do not indicate a safety concern, then pursuing geometric changes strictly to meet design speed is not warranted.
• Bridge deck repair and minor bridge repair projects do not require updating the guardrail and/or safety systems. This remains consistent with current practice.

Design Decision Document

This document shall serve as the design decision for all projects affected by the statutory speed increase. Its guidance is to be applied uniformly to ensure consistent and compliant design practices across all impacted project segments.

Chronology of Changes