a gis-based index for estimating road vulnerability

A GIS-Based Index for Estimating Road Vulnerability to Damage from

Overweight Vehicles

Je r e m y S c o t t

R e s e a r c h As s o c iat e

In s t it u t e f o r T r a n s p o r tat io n

R e s e a r c h a n d E d u c at io n

G r e g F e r r a r a

P r o g r a m M a n a g e r

In s t it u t e f o r T r a n s p o r tat io n

R e s e a r c h a n d E d u c at io n

1

Introduction

• In s t it u t e f o r T r a n s p o r tat io n

R e s e a r c h a n d E d u c at io n (IT R E )

s u p p o r t s N o r t h C a r o l in a S tat e

H ig h way Pat r o l (N C S H P ) M o t o r

C a r r ie r E n f o r c e m e n t (M C E ):

Helping to reduce Commercial Motor Vehicle (CMV) related crashes

preserving the states road and bridge infrastructure

• E n d g o a l : e n a b l e m o r e d ata

d r iv e n in t h e ir e n f o r c e m e n t

e f f o r t s

2

Why Develop a Road Vulnerability Index ( RVI) ?

• M C E p l a n n e r h a s t o

f ig u r e o u t w h e r e t o

s e n d S & W t r o o p e r s

t o c h e c k o n t r u c k s

• R ig h t n o w , H e /s h e h a s

t o l o o k at b r id g e s ,

pav e m e n t c o n d it io n ,

a n d e s t im at e d t r u c k

v o l u m e l ay e r s

s e pa r at e ly.

• RVI w o u l d g iv e t h e m a

s in g l e s im p l if ie d g u id e

t o f o c u s

e n f o r c e m e n t

r e s o u r c e s

3

RVI Model Development

• T h r e e c o m p o n e n t s c u r r e n t ly

m a k e u p R o a d Vu l n e r a b il it y

In d e x (RVI)

Relative Truck Exposure Index (RTEI)

Pavement Condition Ratings Index (PCRI)

Bridge Severity Index (BSI)

RTEI PCRI BSIRVI

α β γα β γ+ +=

+ +4

Road Vulnerability Index

5

RVI

RTEI PCRI BSI

Truck Count

Truck Capacity

Alligator Cracking

RuttingBridge Rating

Bridge Distress

Posted Weight

GIS

Relative Truck Exposure Index ( RTEI)

• M e a s u r e d a s a r at io o f T r u c k

C o u n t t o T r u c k C a pa c it y

t

TRTEI

v=

6

Truck Count

• P o in t l ay e r o b ta in e d f r o m T r a f f ic

S u r v e y U n it at N C D O T

• R e p r e s e n t l im it e d n u m b e r o f

t r a f f ic m o n it o r in g s tat io n s o n

In t e r s tat e s , U S & N C H ig h way s

• O n ly r o u t e s w it h t r u c k c o u n t

in c l u d e d in RVI

• N C D O T h o p e s t o ta g a l l r o u t e s

w it h t r u c k c o u n t in t h e f u t u r e7

Truck Count

• T w o t y p e s o f t r u c k c o u n t s

Primary

Secondary

• P r im a r y r o u t e s u p e r s e d e s

s e c o n d a r y r o u t e

• If m u lt ip l e t r u c k c o u n t s tat io n s

f o r a r o u t e e x is t, av e r a g e wa s

ta k e n8

Truck Capacity

• D e r iv e d f r o m f o r m u l a t o

d e t e r m in e pa s s e n g e r -c a r

e q u iva l e n t f l o w r at e

• P e a k -h o u r fa c t o r (P H F ) a n d

g r a d e a d j u s t m e n t (fG) fa c t o r

a s s u m e d t o b e o n e

• H e av y v e h ic l e fa c t o r (fHV) b e c o m e s

(ET)-1 , a s s u m in g p r o p o r t io n o f

t r u c k s & b u s e s e q u a l s 1

* *pG HV

Vv

PHF f f=

9

Truck Capacity

• Af t e r c o n s id e r in g t h e s e

a s s u m p t io n s , t h e f o r m u l a t o

c a l c u l at e t r u c k c a pa c it y is

• T h e pa s s e n g e r -c a r f l o w r at e s (vp) a n d e q u iva l e n t fa c t o r s (ET) f o r

s p e c if ie d t e r r a in s a r e ta k e n

f r o m t h e H ig h way C a pa c it y

M a n u a l

• λ is t h e n u m b e r o f l a n e s a n d t h e

va l u e 2 4 t r a n s l at e s t h e h o u r ly

t r u c k c a pa c it y t o a d a ily t r u c k

c a pa c it y

*24pt

T

vv

E

λ=

10


• T h e va l u e s c a l c u l at e d u s in g t h e

f o r m u l a in s l id e 5 a r e

t r a n s f o r m e d t o a s c a l e o f 0 -1 0 0

u s in g t h e f o r m u l a

• Lo w e r va l u e s r e p r e s e n t h ig h e r

v u l n e r a b il it y

100 *100max( )

RTEI

RTEI−

11


12

Pavement Condition Rating Index ( PCRI)

• T w o pav e m e n t d is t r e s s e s

c o n s id e r e d t o b e c o r r e l at e d

w it h t h e v u l n e r a b il it y o f a r o a d

t o c o m m e r c ia l m o t o r v e h ic l e s

Alligator Cracking

Rutting

13

Alligator Cracking

• Al l ig at o r c r a c k in g is a l o a d

a s s o c iat e d s t r u c t u r a l fa il u r e

14Source: NCDOT

Alligator Cracking

• M e t h o d u s e d t o c a l c u l at e

Al l ig at o r C r a c k in g b a s e d o n

f o r m u l a o b ta in e d f r o m P M U @ N C D O T

• D e r iv e d f r o m f ie l d s c o n ta in e d in P C S

l ay e r

ALGTR_HGH_ – Severe Alligator Cracking ALGTR_MDRT – Moderate Alligator Cracking ALGTR_LOW_ – Low Alligator Cracking

• C a l c u l at e d o n a s c a l e o f 0 -1 0 0

• Lo w e r va l u e s r e p r e s e n t m o r e

s e v e r e Al l ig at o r C r a c k in g15

Rutting

• R u t t in g is d e f in e d a s h av in g a

s u r fa c e d e p r e s s io n in t h e w h e e l

pat h s o r at t h e e d g e o f pav e m e n t

16Source: NCDOT

Rutting

• M e t h o d t o c a l c u l at e Rutting s c o r e

o b ta in e d f r o m N C D O T

• D e r iv e d f r o m f ie l d c o n ta in e d in

P C S l ay e r

Rutting Code Score

N o n e (N ) 1 0 0

Lo w (L ) 9 0

M o d e r a t e

(M )

4 0

S e v e r e (S ) 0

17


• If o v e r a l l pav e m e n t r at in g < = 5 0 ,

m u lt ip l e d is t r e s s e s in v o lv e d

• Fa c t o r in N C D O T ’s o v e r a l l

pav e m e n t r at in g in t o P C R I

• P C R I c a l c u l at e d o n s c a l e o f

0 -1 0 0* if RTG 50

2 100PCRI

if RTG 502

A R RTG

A R

+ ≤= + > 18


19

Bridge Severity Index ( BSI)

• B r id g e l ay e r o b ta in e d f r o m

N C D O T

• E v e r y b r id g e g iv e n a B r id g e

R at in g (BR)

• F u n c t io n o f t w o c o m p o n e n t s

o b ta in e d f r o m N C D O T b r id g e

l ay e r

Bridge distress (Dj)

Posted weight (Wj)

0.2 0.8j j jBR D W= +20

Bridge Distress (Dj)

• T w o b r id g e d is t r e s s e s d e f in e d in l ay e r

Structurally Deficient (SD)“... if it is in relatively poor condition, or has insufficient load-carrying

capacity. The insufficient load capacity could be due to the original design or to deterioration.” (NCDOT)

A bridge that is SD is given a Bridge Distress value of 100

Functionally Obsolete (FO)“... if it is narrow, has inadequate under-clearances, has insufficient

load-carrying capacity, is poorly aligned with the roadway, and can no longer adequately service today’s traffic.” (NCDOT)

A bridge that is only FO is given a Bridge Distress value of 33

A bridge that is neither SD nor FO is given a Bridge Distress value of 0

21

Posted Weight (Wj)

• D e t e r m in e d b y h o w fa r b e l o w 4 5

t o n s a b r id g e ’s p o s t e d w e ig h t is

• 4 5 t o n s is t h e m a x im u m w e ig h t

a l l o wa b l e in t h e s tat e w it h o u t a

p e r m it

• T r a n s f o r m e d t o a s c a l e o f

0 -1 0 0

• T h e l o w e r a b r id g e ’s p o s t e d w e ig h t,

t h e m o r e v u l n e r a b l e it is t o

o v e r s iz e /o v e r w e ig h t t r u c k s

100max( )

j

j

W

W

22


• C o m b in e in d iv id u a l B r id g e R at in g s

t o g e t h e r t o o b ta in a c u m u l at iv e

B S I

• E n s u r e s a l l b r id g e s in c l u d e d

• Wa n t t o e n s u r e t h at s e g m e n t s

w it h m o s t v u l n e r a b l e b r id g e s

d e s ig n at e d a s s u c h

max

max( )10

j

jj

BRBSI BR

≠

= + ∑23


• C u m u l at iv e B S I s c a l e d t o 0 -1 0 0

u s in g l in e a r t r a n s f o r m at io n



100 *100max( )

BSI

BSI−

24


25

Road Vulnerability Index

26

RVI

RTEI PCRI BSI

Truck Count

Truck Capacity

Alligator Cracking

RuttingBridge Rating

Bridge Distress

Posted Weight

GIS

RVI Integration

• C o m p o n e n t s d e s c r ib e d a r e

c o m b in e d t o o b ta in RVI u s in g

f o l l o w in g f o r m u l a

• In it ia l RVI, c o e f f ic ie n t s a s s u m e d

t o b e 1



RTEI PCRI BSIRVI

α β γα β γ+ +=

+ +

27

Initial RVI

28

Baseline RVI

• B e f o r e d e t e r m in in g w e ig h t s o f

in d iv id u a l c o m p o n e n t s , b ia s

n e e d s t o b e r e m o v e d

• G o a l wa s t o e n s u r e p e r c e n t

va r iat io n in RVI e q u a l ly e x p l a in e d

b y e a c h o f t h e in d iv id u a l

c o m p o n e n t in d ic e s2 2( ) ( )BSI RTEI RTEI PCRIε ρ ρ ρ ρ= − + −

29

Baseline RVI

• M in im iz in g e q u at io n o n p r e v io u s

s l id e r e s u lt s in b a s e l in e m o d e l

Relative Truck Exposure Index (RTEI)

Pavement Condition Ratings Index (PCRI)

Bridge Severity Index (BSI)

2.05* 1.39* 1.96*

5.40

RTEI PCRI BSIRVI

+ +=

30

Baseline RVI

31

Sensitivity Analysis

• S e n s it iv it y a n a ly s is p e r f o r m e d

t o d e t e r m in e h o w s ta b l e t h e

m o d e l is

• Av e r a g e o f e a c h c o m p o n e n t

p e r t u r b e d b y 5 % RTEI PCRI BSI RVI

Percent Difference

μ 91.52 89.92 89.06 90.22

μ[RTEI] + 5% 96.10 89.92 89.06 91.95 1.93%

μ[PRCI] + 5% 91.52 94.42 89.06 91.37 1.28%

μ[BSI] + 5% 91.52 89.92 93.51 91.83 1.79%32

Summary

• D e v e l o p e d m e t h o d o l o g y t h at s h o w s

h o w t o c o m b in e d is pa r at e d ata s e t s t o

p r o d u c e a s in g l e l ay e r f o r

o p e r at io n a l p l a n n in g

• F r a m e w o r k f o r b u il d in g w h e n d ata is

m o r e c o m p l e t e

• T h e m o d e l is p o r ta b l e

• Ad d it io n a l c o m p o n e n t s ?

Geometric design Grade Lane width

33

Questions?

C o n ta c t: j s c o t t @ n c s u .e d u

We b s it e : h t t p ://it r e .n c s u .e d u /va m s

34

a gis-based index for estimating road vulnerability

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