diverging diamond interchange (ddi) · to turn right onto a freeway ramp from the arterial, use the...
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INNOVATIVE INTERCHANGES
Diverging Diamond Interchange (DDI)
What are innovative interchanges? Interchange designs where traffic movements are modified to improve safety, reduce delay, and increase efficiency.
Visit www.virginiadot.org/innovativeintersections to learn more.
I-64 at US 15 (James Madison Hwy), Zion Crossroads, VA
A DDI IS ALSO KNOWN AS:
� Double Crossover Diamond Interchange
What is a DDI? � A grade-separated interchange design where arterial traffic crosses to the other side of the roadway between the freeway ramps
� Vehicles can turn left onto and off freeway ramps without stopping or crossing opposing lanes of traffic
� Right turns onto and off the freeway ramps occur either before or after the crossover intersections, when traffic is on the “correct” side of the road
� Both crossover intersections are signalized
� Interchange can be designed as an overpass or underpass
When should a DDI be considered?
� At locations with heavy left-turn traffic volumes onto and off the freeway ramps
� At locations without adjacent traffic signals or nearby driveways
� At locations where there is limited roadway width for left-turn lanes between ramp intersections and limited right-of-way to expand
What are the benefits of a DDI?
� Improved safety: Reduces the number of points where vehicles may cross paths
� Increased efficiency: Crossovers can operate with only two traffic signal phases, which allows the interchange to handle a greater volume of traffic and operate with less delay
� Easier access to freeway: Design allows traffic to enter and exit the freeway without crossing opposing lanes of traffic
� Cost effective: Since there are no left-turn lanes on the arterial, a DDI can have a narrower cross section and may be more cost effective than a retrofit or new interchange construction
INN
OV
AT
IVE
IN
TE
RC
HA
NG
ES
Nav
igat
ing
a D
iver
ging
Dia
mon
d In
terc
hang
e (D
DI)
V
isit
ww
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irgin
iado
t.or
g/in
nova
tivei
nter
sect
ions
to
lear
n m
ore.
q
Pede
stria
ns u
se m
arke
d cr
ossw
alks
to
safe
ly
navi
gate
the
inte
rcha
nge
g
To t
urn
right
ont
o a
free
way
ram
p fr
om t
he
arte
rial,
use
the
right
-tur
n la
ne li
ke a
t a
conv
entio
nal
diam
ond
inte
rcha
nge
ä
To c
ontin
ue s
trai
ght
on t
he
arte
rial,
follo
w la
ne m
arki
ngs
and
traf
fic s
igna
ls t
o cr
oss
to
the
left
sid
e of
the
art
eria
l, an
d th
en c
ross
to
the
right
si
de a
fter
pas
sing
thr
ough
th
e in
terc
hang
e
h
To t
urn
left
ont
o a
free
way
ra
mp
from
the
art
eria
l, fo
llow
lane
mar
king
s an
d tr
affic
sig
nals
to
cros
s to
the
le
ft s
ide
of t
he a
rter
ial,
and
then
tur
n le
ft o
nto
the
ram
p
NO
T TO
SC
ALE
g
To t
urn
right
fro
m a
fr
eew
ay r
amp,
use
the
rig
ht-t
urn
lane
like
at
a co
nven
tiona
l dia
mon
d in
terc
hang
e
h
To t
urn
left
fro
m a
fre
eway
ram
p,
follo
w la
ne m
arki
ngs
and
traf
fic s
igna
ls
to s
tay
on t
he le
ft s
ide
of t
he a
rter
ial,
and
then
cro
ss t
o th
e rig
ht s
ide
afte
r pa
ssin
g th
roug
h th
e in
terc
hang
e
Ǧ
Dep
endi
ng o
n th
eir
leve
l of
com
fort
, cy
clis
ts m
ay n
avig
ate
the
inte
rsec
tion
usin
g ve
hicl
e or
ped
estr
ian
path
s
No
te: F
or
sim
plic
ity,
on
ly t
wo
dir
ecti
on
s o
f tr
affi
c
are
sho
wn
. Op
po
sin
g t
raffi
c fo
llow
s si
mila
r ro
ute
s.
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