Ch9-1 Types of Intersections

7/24/2019 Ch9-1 Types of Intersections

1/23

Chapter 9: Intersections, p.9-1 ~p.9-28)

Become familiar with general design principles for at-Become familiar with general design principles for at-grade intersectionsgrade intersections

Become familiar with the tpical intersection tpes andBecome familiar with the tpical intersection tpes andtheir characteristicstheir characteristics

!now what the channeli"ation is, o#$ecti%es for &sing!now what the channeli"ation is, o#$ecti%es for &singchanneli"ation, and factors affecting its applicationchanneli"ation, and factors affecting its application

Become familiar with general characteristics ofBecome familiar with general characteristics ofro&nda#o&ts and their applicationsro&nda#o&ts and their applications

Become aware of iss&es related to alignment and profileBecome aware of iss&es related to alignment and profile

Objectives:


2/23

Intersection tpes

'rade separated

(t-grade

ith ramps*Interchanges)

itho&t ramps

*meaning no

connection

#etween the

intersecting

roads+)


3/23

9.2 'eneral esign Considerations and

#$ecti%es *p.9-2)

Need to meet two conflicting objectives:

inimi"e the se%erit of potential conflicts among differentstreams of traffic and #etween pedestrians and t&rning

%ehicles.

/ro%ide for the smooth flow of traffic across the intersection

Main objective: 0acilitate the con%enience, ease, and

comfort of people tra%ersing the intersection while

enhancing the efficient mo%ement of motor %ehicles,

#&ses, tr&cs, #iccles, and pedestrians.


4/23

9.2. esign o#$ecti%es of intersection

design *p.9-3):

Human factors*approach speed, &ser e4pectanc, decision andreaction times, etc.)

Traffic considerations*appropriate capacit, distri#&tion of %ehicletpes and t&rning mo%ements, approach speeds, special treatments fortransit %ehicles, pedestrians, and #iccles)

Physical elements*a#&tting properties, traffic mo%ements generated #them, intersection angle, e4istence and location of traffic controlde%ices, sight distances, specific geometric characteristics)

Economic factors*cost of impro%ements, effects of impro%ements on

the %al&es of a#&tting properties, the effect of impro%ements on energcons&mption

Functional intersection area*operational intersection area incl&dingdeceleration and acceleration "ones as well as 5&e&ing areas) *9.2.2 in'B2611)


5/23

9.2.2 Intersection 0&nctional (rea, p.9-2

conald at B&lldog 7 0reedom


6/23

9..1 (t-grade intersections *pa attention

to channeli"ation techni5&es): or -leg

*p.9-11)

nchanneli"ed

0lared

Channeli"ed


7/23

9..2 (t-grade intersections *pa attention to

channeli"ation techni5&es): 3-leg *p.9-13)


8/23

Contin&o&s flow

intersectionhttp:www.&dot.&tah.go%cfi

T anes

!Ta

nes

Tanes
http://www.udot.utah.gov/cfi/http://www.udot.utah.gov/cfi/


9/23

The "dvantages of #F$

;im&lations &sing e5&ires little more right-of-wa than a con%entional at-grade

intersection.intersection. /ro%ides clear lines of sight, a%oiding the %is&al #arriers created #/ro%ides clear lines of sight, a%oiding the %is&al #arriers created #o%erpasses.o%erpasses.

?elps red&ce poll&tion # red&cing congestion.?elps red&ce poll&tion # red&cing congestion. >e5&ires shorter constr&ction time and less &tilit relocation.>e5&ires shorter constr&ction time and less &tilit relocation.


10/23


11/23

;/I *;ingle /oint r#an Intersection)

https:www.o&te.comwatch@%Amwpo/G1;/
https://www.youtube.com/watch?v=mwpoPQ1SPJUhttps://www.youtube.com/watch?v=mwpoPQ1SPJU


12/23

%&'&' "t(grade intersections )*ay attention to

channeli+ation techni,ues-: Multi(leg )*&%(.%-

&lr ;5&are in

'reenwich


13/23

9..3 0rom a circle to a ro&nda#o&t *p.9-21)


14/23

( tpical circle H /lace dJtoile

*/lace Charles de 'a&lle)


15/23

pical marings for ro&nda#o&ts with one lane

>o&nda#o&ts H different from circles

K

Circles ma ha%e asignal, ;/ signs, no-

control at entr H

>o&nda#o&ts are

alwas controlled #

Field signs.

K;plitter islands

K/eds are not allowed

to &se the central island

K

Eo paring in thecircle

KCirc&lating %ehicles

alwas ha%e the >.


16/23

>o&nda#o&ts from C


17/23

>o&nda#o&ts H different from circles

In (&stralia

In arland In Eorwa

(d%antages:

/ro%ides non-stopmo%ements

>ed&ce crash

occ&rrences

>ed&ce crash se%eritJstheticall appealing

0&nction as a traffic

calming meas&re

'ood for low tomedi&m traffic.

efinitel E for

high %ol&me

intersectionsoo

man wea%ings in ashort distance


18/23

;ometimes pro#lems e4istL

Mehi >o&nda#o&t

rong sign tpe

hen a train

comesL

Correct one is shown here.


19/23

/ro#lemsL ?ow do we pro%ide safe

crossing to pedestrians

/ar Cit >(

(

here does the pedestrian

crossing end@

he signs sa no pedestrian

crossing, #&t where can the go@


20/23

th#&sters 3 wa stop %s.

ro&nda#o&t

https:www.o&te.comwatch@%A>"5>BtnJ>8
https://www.youtube.com/watch?v=RzqJRBtnER8https://www.youtube.com/watch?v=RzqJRBtnER8


21/23

9.3.2 (lignment *p.9-2)

(c&te angle*see p.81)

#t&se angle

he angle of

t&rns sho&ld

#e N6 to 126

degrees.

;&ggested impro%ements to

intersections with ac&te OangleP

pro#lems

Monger waling

distance

ider pa%ement needed for t&rning%ehicles #eca&se of off-tracing

;&perele%ation

pro#lem

(ngle of t&rn


22/23

9.3. /rofile at intersections *p.9-2Q)

ae it as flat as possi#le

(%oid approach grades in e4cess of =

(%oid grade changes at intersections *Crest sight

distance pro#lems, ;agdrainage pro#lems)

he grade line of the ma$or highwa sho&ld #e carried

thro&gh the intersection. (d$&st the grade for the normal

crown of the crossroad to an inclined cross section at its

$&nction with the ma$or road.J4ample in the ne4t slide

J4ample: E. ni%. (%en&e 7 B&lldog

Bl%d. hich street has the normal

crown ept thro&gh the intersection@

Can o& see this little pond ofwater@


23/23

Col&m#ia Mane and 'rand%iew >oad *the

signali"ed intersection on Col&m#ia Mane $&st

north of I). Col&m#ia Mane is the ma$orroad at this intersection and

its grade is ept. Beca&se

there is a normal crown, the

stop #ar on the far side

cannot #e seen.

he cross slope of the minor street is

ad$&sted to the slope of Col&m#ia Mane.

hen o& ha%e time, dri%e there to see

how pa%ement s&rface is ad$&sted for

main line grade.

Documents

Ch9-1 Types of Intersections