2010.11.09.

1

ROADSROADSTRAFFIC CONTROL

LECTURE 8

TRAFFIC CONTROL requires sending messages to the driver

On-board intelligent devices give PERSONALIZED information

basically information and guidance

not suitable for obligatory orders

not mounted in every vehicles

could be switched off

2010.11.09.

2

VISIBLE, easily INTERPRETABLEroadside signs

road type signs

right-of-way signs

directing signs

prohibitive signs

danger showing signs

informational signs

directional signs

Traffic signs

ROAD TYPE SIGNS

repeated after each intersection

before the end preliminary sign is needed

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RIGHT-OF-WAY SIGNSplaced to the stop line

not obligatory to stop obligatory to stop

in case of bad sight conditions

DIRECTING SIGNS

circular signs with blue background

signing of direction, minimal speed or road use

PROHIBITIVE SIGNS

circular signs with red edge

prohibition or limitation of stopping or driving

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4

DANGER SHOWING SIGNS triangular signs with red edge

150-200 m from the location of the danger

INFORMATIONAL SIGNSrectangular signs with

blue background

lane configuration signs are important from the point of view of understandability of the intersection

SUPPLEMENTARY signsdirectly under the supplemented sign

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VARIABLE MESSAGE SIGNS

display of varying signs and texts

dynamic traffic control

DIRECTIONAL SIGNS

directional, preliminary signs are needed

confirmatory

Location of directional signs should not decrease the SIGHT CONDITIONS of the intersection

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6

DESIGN PRINCIPLES

of traffic signs

Traffic signs should be placed always on the RIGHT SIDE

could be repeated on the left side or above the road

if the sign on the right side could not be seen because of the tucks

Exception:one-way road or signs by lanes

No more than 3 signs on one column

or the interpretation is difficult

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Signs should be LIGHT-REFLECTING

significantly increase the visibility in darkness

dashed line

continuous line

optical line

area closed for traffic

stop line

directional marks

crossings

Road marks

DASHED LINE

center line, if the pavement is at least 5,50 m wide

edge of traffic lanes

safety line for turning movements in intersections

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8

CONTINUOUS LINEprohibited to cross or touch

only if it is reasoned from traffic safety aspects

lane change prohibition

overtaking prohibition

separation of opposite flows

CROSSABLE CONTINUOUS LINE

crossable from the side of the dashed linedashed line and continuous line beside each other

application: overtaking is prohibited from only one

of the directions access to properties

OPTICAL LINE

continuous if the pavement is wider than7,00 m

optical guidance

dashed at turning main road

not applied beside curb

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9

PEDESTRIAN CROSSING

stripes are parallel to the road

crossing angle> 60

could be broken only if there is an island at the break

width:+= nnSz ,50.100.3

AREA CLOSED FOR TRAFFIC

bordered by continuous line on both sides

stripes slanted in case of similar

direction of traffic V-shaped in case of opposite

direction of traffic

STOP LINEstop lines could be pulled away from each other

continuous STOP signalization

dashed yield

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10

DIRECTIONAL MARKSonly in lanes signed by pavement marks

wrong right

sizeline/gap

VISIBILITY of pavement marks could be increased by light-reflecting prisms

Pavement marks could also be VARIABLE

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11

Signalization

INTERSECTIONS

STOP-controlled intersections

Roundabouts

Separated intersections

Signalized intersections

By the increase of the volume and speed

of the traffic, the STOP-control works with

decreasing efficiency

other solutions are required

Signalization Separated intersections

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12

Signalization is applied,

if STOP-control can not provide

suitable traffic operation

OR

the intersection is dangerous

The essence of signalization

is to let the traffic

go through the intersection

ALTERNATELY

At STOP-CONTROL

the major flow

goes without disturbances,

the minor flow uses

the available gaps

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13

As the volume or speed of the

traffic increase

the availability of suitable gaps

decrease

delay increases

queues are formed

The vehicles of the minor flow

SHOULD BE ABLE TO GO

through the intersection as well

signalization

Signalization

collects the

gaps useless for minor flow and

allocates them together

Signalization compress the traffic flow

The total delay of the minor flow decreases more than the one of the major flow increases

The major flow is not undisturbed anymore!!!

BUT

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14

The intersection is

DANGEROUS

due to the bad sight conditions

SAFE CROSSING

should be provided

for the vehicles of the

minor flow

signalization MAKES the other

directions TO STOP,

so the crossing is safe

By signalization the intersection

becomes safer and its capacity

increases

not always true comparing to roundabouts

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15

The SIGNS of the traffic lamp

determines when it is

possible to enter

into the intersection

GREEN TIME

free sign, it is possible to enter

The flashing green sign of the pedestrian lamp does not really belongs to the green time, but pedestrians can enter

There is flashing green in Austria

RED TIME

it is not allowed to enter into the

intersection

transition time, for safe emptying of the intersection3-5 mp

preparation time, for starting at the first second of green, 2 mp

flashing green, transition time, 5 mp

not in the USA

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The sequence of signs is called CYCLE

Cycle

The sequence of signs for each lamps

is shown in the SIGNALIZATION PLAN

lost time

cycle length

greenredyellowred-yellowflashing green

Determination of LOST TIME

time of emptying

time of entering

lost time

s

m15 ],[ == sms

lt bb

s

m10 ],[ == sms

lt

timetransition+= bk ttt

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17

TRAFFIC CONTROL BY LANES

Separated signal for each lane

Conflict-free crossing is provided!Arrow

shaped sign

TRAFFIC CONTROL BY

DIRECTION

Identical signal for each lane of the

direction

Full green

Conflict between left turning and opposite vehicles!

The signal on the right is the primary one, regards all the lanes

Other lamps repeat this signal

WHERE to place the lamps?

mounted

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The flows not crossing each other can

use the intersection

simultaneously

this set of conflict-free flows is called

PHASE

PHASE TIME

while the movements of the phase can

enter into the intersectionNot necessarily equals to the green time!

Phase 1 Phase 2

Right turning movement can belong to both phases

Two conflicts are allowed in phases:

1. left turning vehicles cross

the opposite floe

2. right turning vehicles cross

the parallel pedestrian flow

full green

sometimes left turning

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19

The crossing the left turning vehicles

and the opposite works only,

if the volume of the opposite flow is

LOWthe vehicles do not disturb each other, there is no impedance

Good example: Csky utca Bartk Bla t

Bad example: Kiscelli utca Bcsi t

The pedestrians IMPEDE significantly

the operation of vehicles crossing

them!It is possible that no vehicle can go through during the green time!

Bad example: Csky utca Bartk Bla tReason: long walking distance

Bad example:Jzsef krt Baross utcaReason: too many pedestrians

Good example:Budafoki t Bertalan Lajos utca

HOW TO CREATE THE PHASES?

The design volumes of the

movements in the phase should be

approximately the SAME

This means that the volume of the lanes should be more or less equal in a phase

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EXAMPLE:

first phase sequence

Phase 1Phase 3

Phase 2 Phase 4 120

100

7550

700

65075

600

650

100 350300

50

320 300

50

700+75+350+120 = 1245 j/h

EXAMPLE:

second phase sequence

Phase 1Phase 3

Phase 2

Phase 4

120

10075 50

700

65075

600

650

100 350300

50

320300

50

700+75+350+320 = 1545 j/h

What is the REASON of the difference?

Phase 3

Phase 4

120

100

350300

50

320 300

Phase 3

Phase 4 120

100

350300

50

320 300

Sequence 1 Sequence 2

Lanes of lower volume are in the same phase

Lanes of higher volume are in the same phase

Lanes of higher and lower volume are in the same phase

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The phase sequence

DETERMINES

the capacity of the intersection

to a great extent!

WHAT IS THE CAPACITY OF THE

INTERSECTION?

There are simple and complex

calculations

The gap between the vehicles

should be at least 2 s

1800 vehicles

can operate in one lane

in 1 hour

It is not really true, but it is a good approximation for now

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22

At the CHANGES OF PHASES the

vehicles can not enter into the

intersection this time is lost

Only the part of the cycle length

REDUCED by the sum of lost time

could be used to enter into the

intersection

= kipzi ttt

The sum of lost times depends on the phase sequence!

sum of green times cycle length

sum of lost times

CAPACITY of one cycle:

tp

kipi Ft

ttF

=

sum of the highest volumes of lanes in phases!!!

cycle length

green time

saturated volume1800 pcph

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The MINIMAL CYCLE LENGTH:

t

i

kip

FF

tt

=

1min,

t

i

p

ki

p

ki

t

i

tp

kipi

FF

t

t

t

t

FF

Ft

ttF

=

=

=

1

1

For better level of service the

minimally necessary cycle length is

INCREASED

min,min,max, 120 pppp tttt ==

geometrical mean of maximal and minimal cycle lengths

The green times are allocated among

the phases in relation to the design

volumes of the phases

( )

= kipi

iiz ttF

Ft

,

sum of green times

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CAPACITY of signalized intersections

according to the Hungarian standard:

;120

1 20

=

p

ktgy t

tFK

;55,1

10

+=

p

ktopt t

tFK

Practical time span(5 years)

Optimal time span(15 years)

Here the minimal cycle length increased in a greater extent

Lost time is increased by the ratio of maximal and minimal cycle lengths

the maximum flow is decreased by the ratio of the total lost time

The capacity of the signalized

intersection assuming general values:

Kopt Kgy

2 phases 1400 1500

3 phases 1250 1400

4 phases 1100 1250

tp = 90 s tki = 5 s

Above the features of

a PRE-TIME signalization

was discussed

operates based on the design

volumes, does not take into

account the actual traffic

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TRAFFIC ACTUATED

SIGNALIZATION

The green times of phases are

MODIFIED according to the actual

traffic demands cycle length changes as well!

could be combined with control of other transport modesfi. trains

Vehicles are detected by DETECTORS

located 20-60 m from the stop line

not too close, not too farPedestrian button is one type of

detector

bus detection as well

Each phase requires a

MINIMAL GREEN TIME

if there is no demand in a given phase then the phase could be eliminated

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In case of demand

the green time of the phase could be

extended,

but switch is needed at reaching the

MAXIMAL PHASE TIME

the other flows should have the opportunity as well!

Start of the phase

Any

vehicle?

Minimal green time

Next phaseextension of green

time

Any

vehicle?

max.

green

time is

over?

n

y

n

ny

y

Minimal green time is provided for phases

Green time is extended if needed (usually. 2 s)Phases could

be eliminated

CENTRAL SIGNALIZATION

Signalization of intersections is

controlled from a center based on the

actual traffic demand

Use of several pre-timed programs

Cycle length is the same in the whole system

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By coordinating the signalization of

adjacent intersections the vehicle columns

of the major movement(s) could be kept

IN MOTION along longer sections

Delay decreases significantly! It is not needed to make standing column to move again and again!

The cycle length should be the same in the whole system!

time

dist

green time offset

The essence of PROGRESSION, that

the vehicles arrives to the intersection

of the lowest capacity reserve IN

MOTIONA lot more vehicle can pass during the green timeTime should be given to the vehicles

waiting at the stop line to start moving

The green time should start sooner than the moving vehicle column arrives

The GREEN TIME of

opposite flows is

OFFSET

The opposite flow has green sign and I could go as well. Why do I have red sign?

That is why

It is possible only if there is capacity reserve

time

dist

green time offset

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SIGNALIZATION

is the base of

urban traffic control,

by its application

the SAFETY and CAPACITY

of the intersections

could be increased significantly

INTERSECTIONS

STOP-controlled intersections

Roundabouts

Signalized intersections

Separated intersections

TRAFFIC CONTROL

Traffic signs

Road marks

Signalization