---
title: "Grade-Separated Interchange"
url: "https://commonwaysystem.org/patterns/intersections/grade-separated-interchange/"
id: "INT-GSI-10"
description: "Freeway-scale intersection treatment, an acknowledged fallback for volume or speed beyond what a turbo-roundabout can manage."
updated: "2026-09-10"
---

# Grade-Separated Interchange

`INT-GSI-10`

Situational / Discouraged Intersections & Crossings

Grade-Separated Interchange

An interchange carrying conflicting movements on separate vertical levels, connected by ramps, eliminating at-grade conflict entirely. Freeway-scale only.

## Related Media

The items below come from outside the Commonway System, external videos, podcasts, and articles related to this page's topic, not part of the guidebook itself.

Aligned

### [Roads don't have to be FAT to be FAST](https://www.youtube.com/watch?v=UV0x2hNRYnU)

Road Guy Rob

Explains the interrupted-flow/platooning physics behind signalized-arterial congestion, then covers Carmel's Keystone Parkway conversion to a limited-access road using compact elevated roundabout interchanges instead of a full diamond interchange.

Typical at: Undeveloped Rural Suburban

Compact and Urban are edge cases. Core is an unlikely pairing.

## Design notes

This is an acknowledged fallback for genuinely Freeway-scale volume or speed beyond what even a turbo-roundabout can manage, not a general-purpose alternative to the Commonway System's roundabout-first intersection philosophy. It stays confined to the density range where full Freeway-scale roads themselves are realistic.[1]

## Related patterns

[Default (Freeway)](https://commonwaysystem.org/patterns/freeways/default.md) (FRE-DEF-01) (reciprocal link to the Freeway-scale pattern this connects into), [Turbo-Roundabout](https://commonwaysystem.org/patterns/intersections/turbo-roundabout.md) (INT-TRB-02) (explicitly named on this page as the tier just below it), [Displaced Left-Turn](https://commonwaysystem.org/patterns/intersections/displaced-left-turn.md) (INT-DLT-14) (the faster, lower-cost alternative often chosen over this pattern at high-volume urban and suburban intersections)

## References

1.  Legal / regulatory [American Association of State Highway and Transportation Officials, _A Policy on Geometric Design of Highways and Streets_.](https://store.transportation.org/Item/PublicationDetail?ID=4127)