Roundabouts & Interchanges

Build a complete roundabout in one click: the ring, its approach roads and, if you like, splitter islands, a road or tram line through the middle (a hamburger roundabout, optionally with experimental traffic lights) and a landscaped centre island. Round or oval, mini or huge, three to six arms. Three more menu entries build a Magic Roundabout (five mini roundabouts around a two-way ring), a Channelized Junction (a T or X junction with slip lanes across the corners) and a Roundabout Interchange (a highway junction with a roundabout on another level). Three more, next to the game's own interchanges, build highway interchanges with one-way ramps: Parclo, Parclo, two quadrants (both partial cloverleafs) and Diamond.

Once placed, everything turns into ordinary roads that you can edit, extend or connect like any other street.

Features

• Better Roundabouts: round or oval (up to 2:1), five sizes from a mini roundabout (XS, 10 m) to XL (60 m), 1, 2 or 4 ring lanes, 3 (T or Y), 4, 5, 6 or no arms, clockwise or counterclockwise. Optional splitter islands, a road or tram line through the centre (a hamburger roundabout, the through road can differ from the arms) and a centre island: grass, grass with trees, a fountain or paving. If the roads you chose don't fit, the ring grows to the smallest size where they do.
• Magic Roundabout: five mini roundabouts on a two-way central ring, after the famous one in Swindon. Five sizes, 1 or 2 lanes on the minis.
• Channelized Junction: a T or X junction with one-way slip lanes across the corners, triangle islands and optional splitter islands on the side road. Five scales.
• Roundabout Interchange: a highway crossed by a roundabout on another level, with four slip roads. Two-bridge ring, dumbbell or peanut; the ring over the highway or the highway over the ring.
• Parclo, Parclo, two quadrants and Diamond: highway interchanges with one-way ramps, the road over the highway or the highway over the road, three scales and three ramp lengths.
• Right- or left-hand traffic on every entry. Bridges are steel before 1970 and concrete after.
• Raised builds: the setting Structure on every entry. Embankment (the default for roundabouts and the Channelized Junction): the roads lie on the ground, and raised with the game's Height control they stand on earth fill. Bridge (the default for the interchanges): every road is a bridge, so the ramps stand on pillars instead of earth banks, and a raised roundabout or interchange leaves the ground below as it is. Stone bridges before 1970, concrete with short spans after. Bridge builds have no centre, splitter or corner islands.
• Experimental: traffic lights at the ring entries, or where a through road crosses the ring.
• Uses only base-game roads, trees and models.

Supported roads

• Town and country roads, small, medium and large, for arms, through roads, main and side roads and cross roads.
• Highways, small, medium and large, built as two one-way carriageways (Roundabout Interchange, Parclo, Diamond).
• One-way roads for the rings, splitter lanes, slip lanes and ramps: the game's own, the same ones as the built-in roundabout.
• Tram tracks: on the ring and every arm, or a tram line straight through the centre.

The settings sit in the panel on the left of the screen while you place an entry; each setting's tooltip explains it. S, M, L mean small, medium, large; XS and XL extra small and extra large.

Companion mods: Smart Lanes and Bulk Bulldozer

Roundabouts & Interchanges pairs well with two separate mods of mine. To get them, view my other mods (click the creator name, square) and subscribe. Each mod works independently, so you can use any of them on its own.

Smart Lanes: with it, every multi-lane roundabout, splitter island and slip lane you build here gets proper lane discipline straight away: entry and exit lanes matched one to one, and the outer ring lane exiting at the next exit. Without it, the game's own lane settings apply.

Bulk Bulldozer: a bulldoze brush for easy clean-up. Once built, a roundabout is many separate road pieces. To replace an old junction, or to rebuild a roundabout with other settings, paint over it with Bulk Bulldozer, check the red highlight and cost, and remove it all in one go instead of piece by piece. Find it in Road → Tools.

Notes

• Find "Better Roundabouts", "Magic Roundabout", "Channelized Junction" and "Roundabout Interchange" in the road construction menu next to the built-in roundabout. "Parclo" and "Parclo, two quadrants" are next to the game's cloverleaf, "Diamond" next to the game's diamond interchange. All seven are available from 1940 (the game's own interchanges from 1960). The mod's menu icons carry a small badge so you can tell them from the game's.
• Rotate it while placing with the game's usual construction rotation keys. The arm ends are loose road ends: connect your roads to them.
• The roundabout cannot be reconfigured after it is built, because it has already become plain roads. Bulldoze and place it again to change it.
• The Channelized Junction, the Roundabout Interchange and the three highway interchanges have been checked against the game's placement check on flat ground, less thoroughly than the roundabouts: if a combination says "Construction not possible", try other spacing (another scale or ramp length) or another road type. The highway interchanges are large, especially at Scale L: leave room around them.
• Adds nothing to the game but seven construction menu entries and the short-span concrete bridge they use, and runs no scripts while you play. Safe to add to an existing save. If you remove the mod, the roads stay; centre islands that were placed may be missing.

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Changelog

Revision 9 (2026-10-22)

• New: setting Structure on every menu entry, Embankment or Bridge. Embankment builds exactly as before and is the default for the roundabouts and the Channelized Junction; the interchanges default to Bridge. Bridge puts every road on a bridge (stone before 1970, concrete with a pillar every 12 to 24 m after), for a build raised with the game's Height control: no earth fill, the ground stays as it is. Bridge builds have no centre, splitter or corner islands. Your saved settings and the roads you already placed are not affected.

Revision 8 (2026-10-14)

• The highway interchanges (Parclo, Parclo, two quadrants, Diamond) now come right after Roundabout Interchange in the street constructions menu, before the base game's interchanges.

Revision 7 (2026-10-12)

• Fixed: some small one-lane ovals with wide arms (town or country large, a few town medium) on T, Y or X layouts without splitter islands could not be placed ("Construction Not Possible"): the wide arm met the ring's outer kerb behind its node at the oval's tight end. These ovals now grow until the arms fit, by one to three radius steps. Every other layout is unchanged, and roads you already placed are not affected.

Revision 6 (2026-10-10)

• New: Channelized Junction setting Scale, XS, S, M, L or XL. XS (the default) is the junction as before, the smallest the chosen roads allow; larger scales set the slip lanes about 1.25, 1.5, 2 or 2.5 times as far out, for bigger triangle islands. The larger scales have not been checked against the game's placement check yet.
• Changed: every menu entry's size setting is now called Scale: Radius on Better Roundabouts and the Roundabout Interchange, Size on the Magic Roundabout. Same buttons, values and defaults: your saved settings keep their meaning, and roads you already placed are not affected.

Revision 5 (2026-10-10)

• New: translations into Russian, German, French, Spanish, Italian, Dutch, Polish, Portuguese (Brazil), Japanese, Korean and Chinese (Simplified and Traditional). The mod follows the game's language setting.
• Changed: the size buttons (XS, S, M, L, XL), the layout buttons (T, X, A, B, AB) and the button labels stay short in every language, so they still fit the settings panel.

Revision 4 (2026-10-09)

• New: three highway interchange menu entries next to the game's own: Parclo (Layout A or B), Parclo, two quadrants (Layout A, B or AB) and Diamond. The road over the highway or the highway over the road, three highway sizes, three scales, three ramp lengths, right- or left-hand traffic. Steel bridges before 1970, concrete after.
• Changed: the mod is now called Roundabouts & Interchanges (was Better Roundabouts). The Better Roundabouts menu entry keeps its name.
• Changed: the settings now sit in the panel on the left of the screen, so the menu's hover tooltip no longer covers them.
• Changed: shorter button labels that fit that panel, explained in each tooltip: S, M, L for small, medium, large (Highway, Scale), CCW / CW for counterclockwise / clockwise, Right / Left for the traffic side, and Level is now On top: Road or Hwy (Ring or Hwy on the Roundabout Interchange). Arms, Through the centre, Slip lanes and the Roundabout Interchange's Layout are now drop-downs. Ring-entry Traffic lights read Off / On. Same choices, same order: your saved settings keep their meaning.
• Changed: every setting that was a slider is now a row of buttons. Radius: XS 10, S 15, M 20, L 35 or XL 60 m on Better Roundabouts, S 15, M 20, L 30 or XL 45 m on the Roundabout Interchange. Shape, Magic Roundabout Size (now XS, S, M, L or XL, the same sizes), Arm length and Slip road length keep their values as buttons.
• Changed: every size setting now starts at its smallest value: Radius XS (10 m) on Better Roundabouts, Size XS on the Magic Roundabout, Radius S (15 m) on the Roundabout Interchange and Scale S on the highway interchanges. The last radius you picked is not carried over once. The other settings keep your last choice. Roads you already placed are not affected.
• Changed: the menu icons carry a small mod badge.
• Changed: nothing else. Every roundabout, junction and roundabout interchange builds exactly as in revision 3.

Revision 3 (2026-10-08)

• New: Channelized Junction menu entry. A T or X junction with one-way slip lanes across the corners (near-side corners or all turns off the main road), triangle islands, optional splitter islands on the side road, for right- or left-hand traffic.
• New: Roundabout Interchange menu entry. A highway with a roundabout junction on another level and four slip roads: two-bridge ring, dumbbell or peanut, ring over highway or highway over ring, small, medium or large highway. Steel bridges before 1970, concrete after.
• New: hamburger roundabouts. Better Roundabouts setting Through road picks the road through the centre separately from the arms, so a larger road can cut through the ring (the ring grows to fit).
• New: Through the centre value Road + traffic lights (experimental): the road through the centre with traffic lights where it crosses the ring, from 1950.
• New: gallery slides for the new entries and a hover preview picture of its own for each menu entry.
• Changed: the Arm road setting now comes right after Splitter islands. Saved settings are kept.
• Changed: 2:1 oval roundabouts with 4 ring lanes, large arm roads, splitter islands and 3 (Y) or 5 arms now set their splitter islands square to the ring's edge, so they fit (before, they were built too large or did not place). Every other roundabout placed with revision 2 settings builds exactly as before.

Revision 2 (2026-10-07)

• Changed: Magic Roundabout sizes Large and Very large are much bigger, with mini roundabouts of 20 and 35 m (were 15 and 20 m). Very large is now about twice as wide as Small. Large arm roads now fit from Large instead of Very large.
• New: Magic Roundabout setting Mini roundabout lanes, 1 (default) or 2. 2-lane mini roundabouts need size Large or bigger.
• Changed: the Direction setting now reads Clockwise / Counterclockwise (was Anticlockwise). Same behaviour and default.
• Changed: building and previewing roundabouts with splitter islands is about three times faster.

Revision 1 (2026-10-07)

• New: first release. Better Roundabouts (round or oval, 8 to 60 m, 1, 2 or 4 ring lanes, up to six arms, splitter islands, a road or tram line through the centre, centre islands) and Magic Roundabout (five sizes).
• New: tram tracks on the ring and every arm, and experimental traffic lights at the ring entries.