Vehicle - Road Interaction, Granlund WSP, NVF Via Nordica 2016 Trondheim

Author: Johan Granlund
Presented by: David Gullberg
Vehicle – Road
Interaction
NVF Via Nordica 2016-06-09
Photo: Stein Johnsen

Overview
Traffic safety risks with EU-semitrailers on slippery roads.
Safety gains for heavy trailers from increased crossfall in road curves.
C/B-analysis: Increasing crossfall is profitable.
Wide shoulder: Effective “barrier” to crashes.
Sweden implementing new pavement condition parameter in 2016.
Improved heavy vehicle safety by increased lane widening in curves.
Road wear from heavy vehicles.
Cutting fuel consumption tenfold per cents, by repair of road damages.
Via Nordica 2016: Vehicle - Road Interaction

-Traffic safety risks with
EU-semitrailers on slippery roads
 Jamming upgrades.
 Jackknife & trailer swing crashes.
 Loss of control due to 5´th wheel lock-up at junction in curve.
-Efficient road maintenance reduce the problems!

EU-semitrailers jamming upgrades
YouTube-video: Foreign Truckers on Norwegian Snow

Bogie axle lift prevents jammed upgrades
1929: First Volvo with bogie was LV64 Long-Frame.
WWII: Zeta-lyften increased maneuverability.
Bogie axle lift in use for increased hill climbing
performance on icy Nordic roads since 70 years.
No report on axle lift causing pavement damages at
icy stiff-frozen upgrades.
Conclusion: Minimize jamming upgrades, by stipulating
bogie-axle tractor units for EU-semitrailers on Nordic roads.
Future risk:
-Climate change results in icy surface, despite non-frozen road?
Solution to prevent road damages:
-When resurfacing roads, add extra bearing
capacity (thicker asphalt, etc.) at severe upgrades.

EU-semitrailer crash type 1: The jackknife
Solution:
Redesign of road surface slopes.
Slopes giving acceptable runoff,
with minimal need for filling and
asphalt milling, are Computer Aided
Designed in 3D.
After the adjustment, a new wearing
course is paved on correct slopes.
YouTube-video “Amazing car driver avoids collision with oncoming lorry“
At rainfall, the water film is thickest at
crossfall transition sections with low
hilliness and thus low drainage gradient.
These outer-curve sections give
dramatic drops in hydroplaning speed.
A wide “pool” allows the vehicle to
rotate much, before recovering grip.

EU-semitrailer crash type 2: Trailer swing
Example: Collision on Hw 50 at Mogetorp (Örebro/Nora)
One died and three were injured when
the EU-semitrailer swung at the slippery
Hw 50.
The 5th wheel had high friction.
The plate around kingpin showed traces of
wear in naked metal, instead of an even
layer of winter-grease.
Photo: B. Eklund
Solutions:
-Increased road friction by ploughing & gritting.
-Reduced 5th wheel friction by proper use of
winter grease.

Photo: Per Thomson
Junction in horizontal curve:
Slope variance cause 5´th wheel lock-up (1)

Skid crash at low speed, as the rig started from stop and turned left.
Photo: Trafikverket PMSv3
Photo: Corren
Junction in horizontal curve:
Slope variance cause 5´th wheel lock-up (2)
6.6 % crossfall in the junction.
This exceeds the limit max of 5.5 %
for tight curves with high speed.
Solutions:
 Move junction from the curve?
 Carefully redesign the crossfall!

NVF Vehicles and Transport seminar
Traffic safety risks with EU-semitrailers on slippery roads
 Held in Karlstad, Sweden, Nov 11th 2015.
 Attendees from Norway, Sweden, Finland, Denmark, Pharoe Islands
& Germany.
 Data showed that EU-semitrailers with short tractor units are up to
300 % more dangerous, than longer Scandinavian heavy vehicles on
the more hazardous slippery Northern roads.
Summary of the seminar is available at NVF website:
http://www.nvfnorden.org/hemsida/utvalg/ts-risker-med-eu-trailer-pa-hala-
vagar/

Vision Zero requires focus on the rollover crashes
Less than 5 % of the heavy goods vehicle crashes are rollovers.
Photo: Volvo Trucks
Data source: Volvo crash
investigation commission
Crashes with severely injured truck
occupants. n = 1500
Data source:
Rollover of Heavy Commercial Vehicles, UMTRI
Percentage rollovers and injury severity among drivers of
semitrailer rigs in USA; 5 years data.
But…
-Rollover is the crash mode where most truck drivers/passengers
are severely injured!
There are annually about 650 rollovers among heavy trucks
with Swedish license plates; almost two per day.

Certain semitrailers are especially sensitive
to adverse cambered curves
Foto: CVDC
De Pont & Milliken, HVTT6
A high center-of-gravity gives rollover-prone vehicles.
Winkler (2000) notes that the most vulnerable are among 5-axle semi-trailer rigs,
loaded to the maximum weight of goods with low density.
These show Static Rollover Threshold (SRT) down to only 0.25.
More recently developed rigs with double floors may be even worse,
when heavily loaded on the upper floor and unloaded on the lower floor.

Influence of CoG & split friction
Road design codes world wide are based on improper analysis of comfort and skid
risk in low passenger car on pavement with homogeneous friction.
Granlund, Haakanes & Ibrahim (HVTT13, 2014) analyzed risk for both skidding and
rollover with heavy vehicles and on split friction road surface:
 Rollover risk in narrow ramps and roundabouts, unless proper crossfall.
 Rollover risk in adverse cambered curves.
 Substantial increase in skid risk as heavy vehicle rolls sideways.
 More hazardous with lower road friction in the outer wheel path.
Photo:VolvoLastvagnar
Figure: Trafikverket
Typically, the center of gravity height and lateral position (load
distribution, too weak lashing, weight transfer) in the trailer and
rearward amplification are crucial for the rollover risk.

The timber trailer rollover at E6
The Accident Investigation Board Norway contracted
WSP/Advantia for:
 Evaluation of road design codes (SE, NO) for ramps.
 Laser scanning of road geometry and road condition.
 Evaluation of the vehicle and reconstruction of the
crash, by use of a TruckSim model of the vehicle.
Foto: Stein Johnsen
Several issues with the road design codes were identified.
The investigated ramp had poor geometry:
 steep downgrade,
 sharp radius, and
 improper crossfall.
The truck had Static Rollover Threshold (SRT) 0.46 g and the trailer 0.40 g;
better than the SRT Minimum 0.35 g limit used in Australia.

The timber trailer rollover at E6 (2)
This WSP/Advantia animation shows reconstruction of the rollover at
the trucks recorded speed profile.
The truck top speed in the crash ramp was 49 km/h.

The vehicle combination´s max safe speed in the E6 ramp was calculated by increasing
speed, from low until reaching Load Transfer Ratio = 0.60 at the trailers rear wheels.
LTR 0.60 means that 60 % of the static weight on the inner wheel is dynamically
transferred to the outer wheel. LTR = 1 means wheel lift and eventually rollover.
Max safe speed was determined to 33 km/h; far below the speed limit in the E6 ramp.
This WSP/Advantia animation shows a drive at the max safe speed 33 km/h.

Upcoming requirements for increased superelevation
Swedish Transport Agency is setting up new safety
requirements for roads and streets.
WSP investigated requirements to "minimize roll risk in
curves" and how much larger superelevation that is
needed:
 The crash rate increases by 4 % for each percentage
too little superelevation.
 For roads with speed limit less than 90 km/h, the
relevant criterion in the design of superelevation is
stability of unfavorably loaded heavy trailers on dry
asphalt (rollover) and on icy split friction (skidding).
 Current maximum allowed superelevation in Sweden
is only 5.5 %. This limit should be raised
significantly. For curves at grades, up to 12 %
superelevation is recommended.

Exaggerated cost for increasing the superelevation
Costs were investigated for increasing superelevation, when
resurfacing old roads. Two reports from NTNU, Bogdashova
(2012) and Lofthaug (2012), were found calculating with
sevenfold too high costs on old roads; 3000 kr/m2.
In comparison; the E4 freeway Uppsala - Mehedeby,
including several bridges and intersections, was
constructed at a total cost of 1923 kr/m2.
WSP investigated costs of increasing
superelevation in numerous scenarios for
existing geometries and for target
geometries with up to 8 % crossfall.
Using data from real world road contracts,
an average cost estimate of 400 kr/m2 was
established for increasing superelevation
when resurfacing old roads.

Highly profitable to increase superelevation
The profitability for increasing superelevation was calculated by
comparing road agency costs with societal savings for reduction of
vehicle crashes.
The results show high Net Present Value also at low traffic volumes.

Analyzing the need for increased superelevation (1)
Two firefighters died and
three firefighters were
injured in the hazardous
curve.
Foto: DT / J Svedgård
Data from a laser/inertial Profilometer show the outer curve is adverse
cambered.
Graphical analysis show that outer lane should be banked up from - 1.3
% camber to about + 4 a 6 % superelevation. The outer edge needs to
be raised at least 15 cm.

Analyzing the need for increased superelevation (2)
Calculate the demand for side friction, fs, by using the
formula for balanced side forces “rearwards”.
The Profilometer provides values for radius R of horizontal
curvature and superelevation tan().
Reference speed = Speed limit, converted into SI-unit [m/s].
)tan
2
(α
R*g
ν
fs 
Plot the demand for side
friction along the road.
Compare with design road
friction value; a function of
speed limit, given in road
design codes.
This calculation method can
be used for efficient
analysis of entire national
road networks.

Wide shoulder: Effective “barrier” to crashes
 Wide road shoulders prevent pavement edge deformation.
 Deformed pavement edge cause vehicle lateral buffeting.
 Lateral buffeting cause instability crashes.
Lateral buffeting is extremely hazardous on ice-slippery roads,
as it can trigger vehicle (or driver) to develop a skid.
Photo: Johan Granlund

Wide road shoulders prevent edge deformation
Roads without wide shoulders have regularly
uneven deformations at the pavement edge.
NVF report 04/2012:
An analytical model based on proven
geotechnical method (Terzaghi & Vesic).
0.25 m narrow shoulder can deduct bearing
capacity at the edge to only 45 % of the B.C.
at the road's center line.
Contact pressure during twin 295/60 R22.5
tires, as per COST 334.
Foto: J Granlund

Lateral support increase edge bearing capacity
Key parameters:
 Shoulder width.
 Slope towards ditch.
 Depth of ditch /
Embankment.
 Pavement bearing capacity
(at the road center).
Wide shoulder provides lateral support.
No pavement edge deformation
Access road provides lateral support:
No pavement edge deformation.
Compare with the 7 cm deep depression just in front
of the access road (Note exploded truck tyre).Photo: J Granlund
Photo: J Granlund

About 25 % of heavy vehicle rollover crashes occur at sections with
deformed pavement edge. De Pont & Milliken (2005).
Edge deformation contribute to crashes
The graph shows sum of vertical loads on all
wheels on the right side of a semitrailer rig, which
runs over a deformed pavement edge.
In this case, edge deformation gave +/- 70 %
dynamic loading.
Pavement edge deformations means slope variance that can provide
lock-up effect in semitrailer 5th wheel => increased crash risk.

Sweden implements Cross Slope Variance parameter
The “Rut Bottom Cross Slope Variance” parameter validated:
 RBCSV correlates with roll vibration in vehicles.
 High RBCSV at many crash sites.
 High RBCSV in sections reported by truck driver panel as hazardous.
 On smooth roads, RBCSV is below limit value “Max 0.3 per cent”.
Foto: J Granlund

Photo: M Pettersson, NCC, 2015-11-09.
Repair of edge slope variance

Insufficient lane widening in curve design codes
Sources: FHWA, Teknologisk
Institutt, Statens vegvesen,
Trafikverket
With winter tires on icy road surfaces, the trailer off-tracking is up to
twice, compared to summer conditions.
Nordic curve design codes are valid only for summer conditions.
New curves need double lane widening, compared to current designs.
Many old roads have no lane widening at all!

Cutting fuel consumption by road repair
The Transmit study (2002) indicated up to 40 % increased truck fuel
consumption on paved state roads in bad condition, than on good roads.
On bad roads, truck speed was lower on average but had higher variance.
Speed variance means braking and (energy consuming) acceleration.
Svenson & Fjeld (2012, 2014, 2016) are analyzing the impact of road
properties on truck fuel consumption, much due to braking/acceleration.
Results show most preventable fuel consumption is caused by:
1. Road damages (road roughness).
2. Road class.
3. Horizontal curvature (also influencing sight distance).
4. Vertical curvature (energy recovered at downhills).
Conclusion:
-Repair of road roughness can reduce fuel consumption, by up to tenfold
per cents.

Summary
Traffic safety risks with EU-semitrailers on slippery roads.
Safety gains for heavy trailers due to increased crossfall in road curves.
C/B-analysis: Increasing crossfall is profitable.
Wide shoulder: Effective “barrier” to crashes.
Sweden implementing new pavement condition parameter in 2016.
Improved heavy vehicle safety by increased lane widening in curves.
Road wear from heavy vehicles.
Cutting fuel consumption tenfold per cents, by repair of road damages.

Thank you for your interest!

Vehicle - Road Interaction, Granlund WSP, NVF Via Nordica 2016 Trondheim

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