---
kind: "unit"
title: "23"
title_heading: "Highways"
key: "chI/subchG"
level: "subchap"
label: "Subchapter G"
heading: "Engineering and Traffic Operations"
release: "ecfr-current"
date: "2026-08-27"
url: "https://uscodex.org/cfr/23/chI-subchG"
sections_count: 375
---

# Subchapter G — Engineering and Traffic Operations

Title 23 C.F.R. — Highways › Chapter I — Federal Highway Administration, Department of Transportation

## Contents

- [Part 620 — Engineering](/cfr/23/chI-subchG-part620.md)
- [Part 624 — Interstate System Access](/cfr/23/chI-subchG-part624.md)
- [Part 625 — Design Standards for Highways](/cfr/23/chI-subchG-part625.md)
- [Part 626 — Pavement Policy](/cfr/23/chI-subchG-part626.md)
- [Part 627 — Value Engineering](/cfr/23/chI-subchG-part627.md)
- [Part 630 — Preconstruction Procedures](/cfr/23/chI-subchG-part630.md)
- [Part 633 — Part 633 [reserved]](/cfr/23/chI-subchG-part633.md)
- [Part 635 — Construction and Maintenance](/cfr/23/chI-subchG-part635.md)
- [Part 636 — Design-Build Contracting](/cfr/23/chI-subchG-part636.md)
- [Part 637 — Construction Inspection and Approval](/cfr/23/chI-subchG-part637.md)
- [Part 645 — Utilities](/cfr/23/chI-subchG-part645.md)
- [Part 646 — Railroads](/cfr/23/chI-subchG-part646.md)
- [Part 650 — Bridges, Structures, and Hydraulics](/cfr/23/chI-subchG-part650.md)
- [Part 652 — Part 652 [reserved]](/cfr/23/chI-subchG-part652.md)
- [Part 655 — Traffic Operations](/cfr/23/chI-subchG-part655.md)
- [Part 656 — Carpool and Vanpool Projects](/cfr/23/chI-subchG-part656.md)
- [Part 657 — Certification of Size and Weight Enforcement](/cfr/23/chI-subchG-part657.md)
- [Part 658 — Truck Size and Weight, Route Designations—length, Width and Weight Limitations](/cfr/23/chI-subchG-part658.md)
- [Part 660 — Special Programs (direct Federal)](/cfr/23/chI-subchG-part660.md)
- [Part 661 — Tribal Transportation Facility Bridge Program (ttfbp)](/cfr/23/chI-subchG-part661.md)
- [Part 667 — Periodic Evaluation of Facilities Repeatedly Requiring Repair and Reconstruction Due to Emergency Events](/cfr/23/chI-subchG-part667.md)
- [Part 668 — Emergency Relief Program](/cfr/23/chI-subchG-part668.md)
- [Part 669 — Enforcement of Heavy Vehicle Use Tax](/cfr/23/chI-subchG-part669.md)
- [Part 680 — National Electric Vehicle Infrastructure Standards and Requirements](/cfr/23/chI-subchG-part680.md)