Ana Arranz Cuenca

Director

Road Safety Department

DIFFERENT TYPES OF JUNCTION BEHAVIOURDIFFERENT TYPES OF JUNCTION BEHAVIOUR

FROM ROAD SAFETY POINT OF VIEW. FROM ROAD SAFETY POINT OF VIEW.

SPANISH EXPERIENCE IN STATE ROAD NETWORKSPANISH EXPERIENCE IN STATE ROAD NETWORK

TYPE OF INTERSECTIONSTYPE OF INTERSECTIONS

By separation• At grade (JUNTION)• Grade Separated (INTERCHANGE)

By signalization• Signalized• Not signalized

By channeling• Canalize• Without channeling

By shape (JUNTIONS)• “T” junction• “Y” junction• “Cross“ junction• “X“ junction• Roundabout

R.C.E.

INTERSECTIONS

5.754

(AVERAGE IN LENGTH: 490m)

1- Inventory

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

(AVERAGE IN LENGTH: 490m)

Kilometres 26.051 Km 2.839 Km (11%)

Injury Accidents 85.367 20.146 (23,6%)

Accident Rate 21,4 34,4

Fatal Accident Rate 1,8 2,7

Death Rate 2,1 3,2

Nº OF JUNTIONS: 5.754

SAMPLE COMPOSITION

BY SHAPE OF JUNCTION BY AREA

T 3.078 53,5%RURAL 3872 67,3%

Y 472 8,2%

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

2- Sample

Y 472 8,2%

Cross (+) 668 11,6%URBAN 1244 21,6%

X 49 0,9%

Opened roundabout

334 5,8%CLOSE TO URBAN 638 11,1%

Roundabout 358 6,2%

Interchange 555 9,6%

Others 240 4,2%

WITH LIGHTING 1.706 29,7% WITH TRAFFIC SIGNALIZATION 188 3,3%

UNTREATED 1.910 33,2%

2- Junctions vs. other road sections

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

23,6%15%

20%

25%

Junctions represent 10,9% of the total lenght of the network, but they concentrate about 24% of injury accidents.

10,9%

0%

5%

10%

LENGTH INJURY ACCIDENTS

3- Junctions vs. other road sections

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

34,4

21,4

7,98,4

6

8

10

12

15

20

25

30

35

40

Both Accident Rate and Fatal Accident Rate are higher at junctions than in the rest of the network. If we calculate a ratio with Fatal Accident/100 Injury Accident, in this case the results are that the index is lower at junctions.

21,4

2,71,8

0

2

4

0

5

10

15

JUNCTION CONTINUOUS HIGHWAY SECTIONS

ACCIDENT RATE FATAL ACCIDENT RATE FATAL ACCIDENT/ INJURY ACCIDENT

4- Junction by type analysis

a) Accident figures considering type of junction

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

45,1

42,1

59,2

8,8

9,9

8,1

10,3

7,7

11,0

8,0

10,0

12,0

40,0

50,0

60,0

70,0

Accident Rate Fatal accident rate Fatal Accident/ Injury Accident

Interchanges have the lowest Accident Rate, followed by roundabouts.

X-junction shows the highest Fatal Acc and Injury Acc rate, while roundabout has the lowest rate value.

34,3 34,4

42,1

33,9

24,3

2,63,4 3,7

4,4 4,5

1,22,3

8,1

3,5

0,0

2,0

4,0

6,0

0,0

10,0

20,0

30,0

40,0

c) Interchange by type analysis

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

Diamond 27,91,91,5

2,9

2,3

34,4

2,7

2

2,5

3

3,5

20

25

30

35

40

Trumpet

Clover-leaf

19,1

19,924

1,5

0

0,5

1

1,5

0

5

10

15

20

Diamond Clover- Leaf Trumpet Others

Accident Rate

Fatal accident rate

Average Accident Rate

Average Fatal accident rate

d) T-junction

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

37,039,7

30,2

39,1

32,433,6

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

45,0

ACCIDENT RATE IN T JUNCTION OF INTERURBAN AREA

30

40

50

60

70

80

90

ACCIDENT RATE VS. CHANNALIZATION

When AADT<10.000 veh/day the T-junction shape with better results regarding Accident Rateis the one that has a left turning lane.

When AADT is over 15.000 veh/day, the T-junction shape with better results regarding AccidentRate is the one that has a left turning lane and merging lane.

0,0

5,0

<5.000 5.000-8.000 8.000-10.000 10.000-15.000 >15.000

AADT main road

ACCIDENT RATE IN T JUNCTION AVERAGE ACCIDENT RATE

AADT<5.000 5.000<AADT<8.000

8.000<AADT<10.000

10.000<AADT<15.000

AADT>15.000

Non channelize 38,4 41,5 27,7 40,5 33,9

Channelize and non middle turning lane 41,3 38,9 31,9 34,6 35

Middle turning lane 23,4 23 26,7 78,4 47,4

Middle turning lane and merging lane 34,6 37,4 31,9 35,8 27,9

0

10

20

30

e) Y-junctions

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

7,5

9,9

8

10

12

36

37

38

39

40

In general, Y junctionsbehave worse thanT-type

34,3 34,4

2,6

3,4

0

2

4

6

31

32

33

34

35

36

T Y

ACCIDENT RATE FATAL ACCIDENT RATE

FATAL ACC/ INJ ACC

f) Cross- type intersection

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

70,9

4,7

6

5,5

6,9

5

6

7

8

50

60

70

80

ACCIDENT DATA AT CROSS TYPE INTERSECTION CONSIDERING

60,055,6

44,1

35,829,8

46,1

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

<5.000 5.000-8.000 8.000-10.000 10.000-15.000 >15.000

ACCIDENT RATE IN INTERSECTION + INTERURBAN AREA

Is the type of junction with the highest values of accident rates together with openedroundabouts, espeacilly when considering rural area.

40,1 38,9

4,7

1,3

0,102 0,0850,034

1,3

0

1

2

3

4

5

0

10

20

30

40

50

Interurban Periurban Urban

ACCIDENT RATEFATAL ACCIDENT RATEFATAL ACCIDENT/INJURY ACCIDENTDEATH RATE MIDDLE

<5.000 5.000-8.000 8.000-10.000 10.000-15.000 >15.000

AADT main roadACCIDENT RATE IN CROSS JUNCTION

48,7

42,5

5 4,6

13,3 12,4

0

3

6

9

12

15

394041424344454647484950

With left waiting lane Not left waiting line

ACCIDENT DATA IN CROSS INTERSECTION ACCORDING TO THE TYPE

OF CHANNALIZATION IN RURAL AREA

ACCIDENT RATE FATAL ACCIDENT RATE FATAL ACCIDENT/INJURY ACCIDENT

� X-Type present a high Accident Rate (AR=42).

� However, this type of junction is more secure than

g) X-Type junction:

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

� However, this type of junction is more secure thanopened roundabouts (AR=59,2) and cross-typeintersections (AR= 45,1). These results confirm that theorientation of the branches of the junction has a possitiveeffect on road safety.

� Not statistically significant sample (0,85%)

h) Roundabouts

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

43,7

33,6

20,7

1,0

1,9

0,5

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

0,0

10,0

20,0

30,0

40,0

50,0

ACCIDENT DATA IN ROUNDABOUT OF TYPE OF AREA

Good results for traditional roundabouts buthigh Accident Rate results for the openedtype.

0,00,0

INTERURBAN PERIURBAN URBAN

ACCIDENT RATE FATAL ACCIDENT RATE

39,935,8

41,3

50,3

25,423,7

1,2

4,6

3,21

1,6

0,6

0,00,51,01,52,02,53,03,54,04,55,0

0,0

10,0

20,0

30,0

40,0

50,0

60,0

INTERURBAN PERIURBAN URBAN AREA

ACCIDENT DATA IN ROUNDABOUT OF TYPE OF AREA AND EX ISTENCE OF LIGHTING

ACCIDENT RATE NOT LIGHTING ACCIDENT RATE WITH LIGHTING

FATAL ACCIDENT RATE NOT LIGHTING FATAL ACCIDENT RATE WITH LIGHTING

5- Accident data vs. AADT

a) AADT in main road

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

40,6 39,335,3

34,129,5 8,0

10,0

12,0

35,0

40,0

45,0

50,0

ACCIDENT DATA OF AADT RANGE

In general, when the AADT increases accident rates tend to improve (lower values).

29,5

3,0 3,4 3,0 2,92,2

0,0

2,0

4,0

6,0

8,0

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

< 5.000 5.000-8.000 8.000-10.000 10.000-15.000 >15.000

ACCIDENT RATE FATAL ACCIDENT RATE

Intersections in Urban areasshow the lowest accident rates.

6- Analysis by area

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

33,6

41,1

31,3

3,2

2,5

2,5

3

3,5

30

35

40

45

ACCIDENTALS FUNCTION OF TYPE OF AREA

show the lowest accident rates.

In rural areas, both Accidentand Severity rates are veryhigh (as car speed is aboveurban areas).

1,4

9,4

6,1

4,3

0

0,5

1

1,5

2

0

5

10

15

20

25

Interurban Periurban Urban

ACCIDENT RATE

FATAL ACCIDENT RATE

FATAL ACCIDENT/ INJURY ACCIDENT

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

7- Analysis considering Lightning requirementsand type of area

Significant results only when considering urban areas.

34,2

41,3

32,433,3

37,4

33,9

3,4

2,62,4 2,5

3

3,5

4

30

35

40

45

ACCIDENT OF TYPE OF LIGHTING AND TYPE OF AREA

considering urban areas.

Outside urban areas, the death rate decreases but the values recorded of accident rate increases.

2,6 2,2 1,30

0,5

1

1,5

2

0

5

10

15

20

25

INTERURBAN PERIURBAN URBAN

ACCIDENT RATE WITH LIGHTING

ACCIDENT RATE NOT LIGHTING

FATAL ACCIDENT RATE WITH LIGHTING

FATAL ACCIDENT RATE NOT LIGHTING

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

DESIGN RECOMMENDATIONS:

On behalf the results of the present Intersection Accident Anlysis, the mainrecommendations (considering the type of junction) to incorporate the current knowledge onthe safety performance are:

a) Outside urban areas:a) Outside urban areas:

Four branches junction:

The best type of junction, regardless AADT values, is the interchange. Among this, theclover-leaf type present the lowest accident rates.

Three branches junction:

� AADT< 10.000 veh/day: T-type, channelized and with middle turning lanes.

�AADT>10.000 veh/day: T-type, channelized and with middle turning lanes andmerging lanes.

b) Urban areas:

The type of junction with better results regarding accident rate are illuminatedroundabouts and interchanges.

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

CONCLUSIONS:

• Roundabouts and Interchanges are the two types on intersections that better complywith safety standars (lower accident rates). In the other hand, the worst results arefor opened roundabouts, Cross-type and X-type junctions.for opened roundabouts, Cross-type and X-type junctions.

• Regarding AADT, accident rates decreases when the AADT of the main roadincreases.

• When two roads merge into a cross-type intersection and one of the roads has anAADT of 8.000-10.000 veh/day, it is recommended to adopt an interchange typedesign.

• Roundabouts are a good solution for urban areas but not for rural areas. Openedroundabouts do not behave well in general, but work better in urban areas if theyhave traffic lights to control the movements allowed.

INTERSECTION ACCIDENT ANALYSIS AT THE STATE INTERSECTION ACCIDENT ANALYSIS AT THE STATE

ROAD NETWORK OF SPAIN (R.C.E)ROAD NETWORK OF SPAIN (R.C.E)

CONCLUSIONS:

• T-junctions can be used for a wide range of AADT. However, for AADT<8.000veh/day, the accident rate is lower in Y-type.

• In general, Cross type of intersections are quite unsafe. The main problem is thelenght of the turning lane (too short), when it is recommended to be over 100metres.

• Lightning has effects on safety only in urban areas.

THANK YOU VERY MUCH THANK YOU VERY MUCH FOR YOUR ATTENTION!