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!


http://www.nvfnorden.org/library/Images/Utskott-och-tema---bilder/Fordon-och-transporter/Seminarie/Trafiksäkerhetsrisker-med-EU-trailer-på-hala-vägar/EU-trailer vs LBs.png

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.

Via Nordica 2016: Vehicle - Road Interaction 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.

https://youtu.be/mRhqhSdAg6s?list=FLAlJP86wypaAT8FLV33nvkQ

https://youtu.be/mRhqhSdAg6s?list=FLAlJP86wypaAT8FLV33nvkQ

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/


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.

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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].

)tan2

(αR*g

νf s

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!


Automotive

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