InRoads XM

Superelevation

Lennie TorgersonEngineering Applications Support Team

Basics

Transitions

The wizard

d

ncw

d

e

eb

ewn1

)( 1

Normal crown

Normal crown

Full Superelevatio

n

Circular Arc

Tangent Runout

Spiral Runoff

PS

PSC

PCRunoff

Tangent Runout Tangent to

curve

Spiral curve

Basics

Give ‘em a good ride…1. Curves 1°and sharper Use spiral transition Runoff length = spiral length

2. Unspiraled curves 0°55’ and sharper Runoff length = normal spiral length

3. Standard spirals cannot be attained Use longest of three solutions

Guiding Principles

Spiraled Curves 1° or sharper Use spiral

transition Runoff = spiral

19215.0

4)24(min L

From:Table 5-3ODOT Highway Design Manual2003 English

wdr b

ewnL

max

1)(

AASHTO Wizard – Roadway Designer

AASHTO Wizard

3.5%

AASHTO Wizard

Superelevation Point Controls

Slo

pe

Station

0

0.02

-0.02

0.04

-0.04

Superelevation Diagram - spiral

LETL RETL

CL

PSCPS

Unspiraled 0°55’ and sharper

From:Table 5-3ODOT Highway Design Manual2003 English

Runoff length = normal spiral length

AASHTO Wizard

450

450

Slo

pe

Station

0

-0.02

0.08

Superelevation Diagram – no spiral

LETL RETL

CL

PC

450’

0.02

Non-standard spirals or runoff

From:Table 5-3ODOT Highway Design Manual2003 English

LETL RETL

CL

Relative Gradient – grade difference/runoff

“…the length of the superelevation runoff should be based on a maximum acceptable difference between the longitudinal grades of the axis of rotation and the edge of pavement.”

Relative Gradient – spiral or spiral runoff

r

d

L

we

From my earlier example of a 4°30’ curve, 50 mph, with an 8% super, runoff length of 450’, and 2-12’ lanes rotating about low side ETL:

%43.0'450

%8'24

x

The math

wdr b

ewnL

max

1)(

s

WeL ds 2

AASHTO

ODOT InRoads XM

•Lr = length of superelevation runoff, ft = maximum relative gradient, %•bw = adjustment factor for number of lanes rotated, based upon number of points on template between Pivot and furthest Range Point.•Dp-e = distance from Pivot to furthest Range Point, ft•ed = design superelevation rate, %

•Ls = length of superelevation runoff, ft•s = relative slope, % (same as )•W = distance from ETL to ETL, ft•ed = design superelevation rate, %

Lr = minimum length of superelevation runoff, ftmax = maximum relative gradient, %n1 = number of lanes rotatedbw = adjustment factor for number of lanes rotatedw = width of one traffic lane, fted = design superelevation rate, %

wdepr b

eDL

max

)(

Example

'192%5.02

%8'24

2

x

x

s

weL ds

From my earlier example of a 4°30’ curve, 50 mph, with an 8% super, and 2-12’ lanes rotating about low side ETL:

AASHTO Wizard

192

192

Slo

pe

Station

0

-0.02

0.08

Superelevation Diagram – short runoff

PC

192’

0.02

50%

Relative Gradient – short runoff

r

d

L

we

Example of a 4°30’ curve, 50 mph, with an 8% super, runoff length of 192’, and 2-12’ lanes rotating about low side ETL.

%1'192

%8'24

x

'192%5.02

%8'24

2

x

x

s

weL ds

Exceeds max. relative gradient!

Relative Gradient – short runoff

r

d

L

we

Example of a 4°30’ curve, 50 mph, with an 8% super, runoff length of 192’, and 2-12’ lanes rotating about centerline.

%5.0'192

%8'12

x

w is the distance between the axis of rotation and the edge of pavement (or TL)

Rotation about CL reduces gradient!

Slo

pe

Station

LETL RETL

CL

Superelevation Diagram – CL rotation

InRoads XM Interpretation

InRoads XM Interpretation•Lr = length of superelevation runoff, ft = maximum relative gradient, %•bw = adjustment factor for number of lanes rotated, based upon number of points on template between Pivot and furthest Range Point.•Dp-e = distance from Pivot to furthest Range Point, ft•ed = design superelevation rate, %

wdepr b

eDL

max

)(

Dp-e

bw

ed

max(1st dialog)

(looked up)

Cross Section in Super

Normal crown

Normal crown

Full Superelevatio

n

Circular Arc

Tangent Runout

Spiral Runoff

PS

PSC

PC/PTRunoff

Tangent Runout Tangent to

curve

Spiral curve

Basics - review

Curves 1°and sharper Use spiral transition Runoff length = spiral length

Easy to use AASHTO Wizard without editing

Unspiraled curves 0°55’ and sharper Runoff length = normal spiral length

Edit “Calculated Runoff Length” in Wizard

Standard spirals cannot be attained Use longest of three solutions Edit “Calculated Runoff Length” in Wizard

Guiding Principles - review

Give ‘em a good ride…

Thank you for attending…