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Elevated Diverging Diamond Interchange

In-game title: E1 Diverging Diamond Interchange (due to character limitations)

A variation of a diverging diamond interchange (Wikipedia)[en.wikipedia.org] where the arterial road passes under an E-1 (12m) Elevated highway. More similar to some real-life interchanges (except the highway and roadways are typically separated by shifting the terrain before building the road rather than creating elevated systems or tunnels so that the highway and roadways maintain their overall altitude shortly after the interchange). May also be more convenient for heavier urban areas where highways are routed above the city roads, or near where bridges and other interchanges are nearby enough to warrant continuing the road through as elevated, rather than two directly adjacent shifts in elevation.

See also Biffa's excellent video tutorial (YouTube)


• Safety
• Capacity
• Relatively easy to place
• Relatively easy to configure

vs.:
• Cost
• Requires additional setup each time (not possible to embed configuration)
• Complexity (Time and Layout)
• Relatively difficult to upgrade
• Prone to configuration errors (missing a single intersection, lane incorrect, fixing an accidentally deleted node...)
• May slow some heavy traffic going straight through the arterial road (e.g., no sliplanes)
• US Driver's don't seem to understand them 😉


• Place on your highway network near where you want your arterial road to go. Recommend taking a look at Smart Intersection Builder
• Add more highway to either side (at least 20u total, or 160m), optionally shifting it to a higher or lower elevation level
• Recommend adding at least 14u (112m) to each arterial road, or avoid adding a crossing intersection, for at least a total of 28u from the interchange. The intersection asset has built-in 14u Medium 4-lane roads on each side, you will want to bring them out further before building more.
• Has some Pedestrian crossings setup but you can adjust them or change them to your preferred style.
• Using TM:PE, Place traffic lights at where the roads cross each other on either side. Add the appropriate lane connections using stay-in-lane as well as the direct crossings for each 4-way crossover. Guide forthcoming. Remove all pedestrian walkways that are part of the highway interchange and the Medium 4-lane road where there is already a pedestrian overpass
• Designed with a 14x14 grid or 14x10 grid in mind (see appendices A, B, D)

• Neither Mass Transit DLC nor NexT2 / CSUR Reborn is required, but you may be able to improve the lane math or the thru lanes with four-lane highways (for about 20u on each side) and two-lane highways, for example.
• TM:PE isn't strictly required, either one will work (STABLE or LABS), but you won't be able to configure a proper Diverging Diamond Interchange setup without it, and it may not work optimally.

Alignment is not 100% perfect but each end of the connections should align to right angles, 14u (112m) on both sides of the arterial road, and 10u on each side of the highway, so it should not interfere with your grid or zoning.

Loosely based on Timboh's Diverging Diamond Interchange by @itstimboh