DIAMOND INTERCHANGE VARIATIONS

VARIATIONS IN LANE LAYOUTS OF DIAMOND-STYLE INTERCHANGES

The design of the standard diamond interchange has been modified in various ways, to increase either capacity or flow performance. Most of these variations involve redirecting some movements to the left of other movements flowing the other way.

The demands of the design are complicated if the ramps also carry traffic on frontage roads, or are connected to rebound interchange ramps. There is no difference between the extra movements for frontage roads and the extra movements for a rebound interchange. Both need the variations shown on the right side of the diagram. But the rebound interchange also needs U-turn movements that are not shown on some of the diagrams.

Here are some of the designs that were tried, in the original design form, and with the frontage road flows added. The animations in the diagrams show the typical traffic signal phasing for each design:


TABLE OF DIAMOND INTERCHANGE VARIATIONS

Without
Frontage Roads

With
Frontage Roads

 
Name

Author's Name
Variation

nIS

nPH

Conflicts

Tangle

FR

Conditions

DV

MR

XG

WV

XR

EN

EX

PN

phasing diagrams

1. STANDARD DIAMOND

STANDARD DIAMOND

2 3
(6)
6 6 6 0 0 2 2 0

Storage limits flow

2. SAME, WITH FRONTAGE ROADS

WITH FRONTAGE ROADS

2 6
(3)
10 10 10 4 0 2 2 0

Storage limits flows

3. CONTRAFLOW LEFT

BRAIDED ENTRANCE LEFTS

2 3 6 6 8 0 0 0 2 0

Storage limits exit flow

4. SAME, WITH FRONTAGE ROADS

WITH FRONTAGE ROADS

2 3 10 10 10 4 0 0 2 0

Storage limits exit flow

5. DIVERGING TURNS

BRAIDED LEFTS

6 3
(5)
8 8 6 2 0 0 0 0

Flows not limited

6. SAME, WITH FRONTAGE ROADS

WITH FRONTAGE ROADS

2
(4)
4
(8)
12 12 14 6 0 0 0 1

Flows not limited

7. DIVERGING DIAMOND

BRAIDED CROSS STREET

2 2 6 6 2 2 2 0 0 0

50 percent limit, Storage limits exit

8. SAME, WITH FRONTAGE ROADS

WITH FRONTAGE ROADS

2 3 10 10 6 6 2 0 0 1

Storage limits exit

9. HALF DIVERGING DIAMOND

SINGLE BRAID TURNS

4 3
(5)
7 7 4 2 0 0 0 0

Flows not limited

10. SAME, WITH FRONTAGE ROADS

WITH FRONTAGE ROADS

4 4
8
11 11 10 6 0 0 0 1

Flows not limited

11. SINGLE POINT URBAN (SPUI)

SPUI

1 3
(5)
6 6 8 0 0 0 0 0

Flows not limited, large bridge

12. SAME, WITH FRONTAGE ROADS

WITH FRONTAGE ROADS

1 4
(8)
10 10 16 4 0 0 0 1

Flows not limited, large bridge

Without
Frontage Roads

With
Frontage Roads

 
Name

Author's Name
Variation

nIS

nPH

DV

MR

XG

WV

XR

EN

EX

FR

Conditions

Conflicts

Tangle

PN

KEY:

COMPARING DIAMOND INTERCHANGE VARIATIONS

1. STANDARD DIAMOND

2. STANDARD, WITH FRONTAGE ROADS

3. CONTRAFLOW LEFT

4. CONTRAFLOW LEFT WITH FRONTAGE ROADS

5. DIVERGING TURNS

6. DIVERGING TURNS WITH FRONTAGE ROADS

7. DIVERGING DIAMOND

8. DIVERGING DIAMOND WITH FRONTAGE ROADS

9. HALF DIVERGING DIAMOND

10. HALF DIVERGING DIAMOND WITH FRONTAGE ROADS

11. SINGLE POINT URBAN (SPUI)

12. SPUI WITH FRONTAGE ROADS

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