Mattias Hjort


Picture of Mattias Hjort

Research results from Mattias


Tunga lastbilars däckanvändning och olycksrisk vintertid

In Sweden, it is today regulated that winter tyres must be used on the drive axle of heavy vehicles (total weight in excess of 3,500 kg) during the winter season period, December 1 to March 31, in case of winter conditions. This requirement is based...

Known Roads: real roads in simulated environments for the virtual testing of new vehicle...

This publication presents a project aiming to develop virtual representations of real roads for use in driving simulators. The development was done in order to enable assessments of new systems on existing and well known roads in a driving...

Jämförelse av vinter och sommardäck på barmark sommartid: tester, riskanalys och...

In Sweden non-studded winter tyres has become increasingly popular during the winter season. Since it is allowed to use non-studded winter tyres also during summer time, a large number of drivers choose to do that. The purpose of this study has been...

Kan dubbdäck på cykeln minska singelolyckorna?: friktionstester av cykeldäck i VTI:s...

The purpose of this project was to define a useful methodology for comparing the ice grip of different bicycle tyres and to perform initial measurements. The long term objective is to set up recommendations to winter cyclists regarding bicycle tyres...

Limit handling in a driving simulator

The purpose of this work has been to investigate how the driving simulator performs at the handling limit of a vehicle and improve its function so that the simulator feels and behaves more like a real vehicle when driving on the limit. Tests were...

Test av is- och snögrepp för slitna vinterdäck: jämförelse av olika kategorier av...

This study has measured ice and snow grip for used and new winter tyres, with the purpose to investigate how the road grip on ice and snow for different types of winter tyres degrade by age and degree of wear. In total, 77 tyres have been tested, of...

Developing of a Driver Model for Vehicle Testing

There is today no established automated method for testing vehicles or tyres, and the most common option is using professional drivers for this purpose. The tests are supposed to be fair and repeatable, which means using human drivers for these...

Testing Vehicle Performance on Snow Using Sine with Dwell

Measuring and evaluating vehicle and tire performance in winter conditions are highly motivated by accident statistics. The present paper investigates use of the sine with dwell maneuver in this context. Various aspects of winter testing is...

Validating on-the-limit properties of a driving simulator

The paper describes a validation model for both subjective and objective comparison of on-the-limit properties of a driving simulator. VTI moving base driving simulator, SIM III, has been used with three different versions of VTI’s vehicle model,...

Validation of a basic combined slip tyre model for use in friction estimation applications

Tyre modelling is an important part of understanding and estimating the tyre-road friction. In this paper a basic steady-state tyre model for the combined-slip case is derived. The model is intended to be used in friction estimations applications,...

EDR Pre-Crash Data: Potential For Applications In Active Safety Testing

Passive safety testing has been based on accident research where objective physical evidence can be compiled and analysed when establishing technical test requirements. Active safety tests pose new challenges because objective data is more difficult...

Measuring tyre performance in ESC intervention situations

Fatal accidents during winter time in Sweden are to a large extent due to vehicle spinning. Therefore, it is crucial to analyse and compare vehicle/tyre performance on slippery roads with respect to oversteering. We have performed experimental tests...

Relation between tyre/road noise and ice snow friction of winter tyres

It is often assumed that low noise emission from car tyres implies a sacrifice of frictional properties. This study explores the relation between tyre/road noise with friction coefficients on ice and snow surfaces for a number of winter tyres,...

Towards a method for determining maximum oversteer in slippery conditions

Fatal accidents during winter time in Sweden are to a large extent due to vehicle spinning. Therefore, it is crucial to analyse and compare vehicle/tyre performance on slippery roads with respect to oversteering. In this study, a new test method for...

Improving the realism in the VTI driving simulators: Shake final report

The Swedish Road and Transport Research Institute (VTI) has three advanced moving base driving simulators. The aim of this project was to develop and implement new models concerning vibration, noise and graphics in order to improve the realism in...

Säkerhetsrisker kopplat till däck, fälg och hjul: en litteraturstudie

A literature review about the road safety effects associated with tires, rims and wheels was carried out, where the literature search was done in consultation with the VTI Library and information centre. The outcome resulted in approximately 90...

The Snow Grip of Heavy Vehicle Drive Axle Winter Tyres

Every winter in Sweden, winter roadways pose problems for heavy vehicles. Steep gradients can be difficult to pass when it is slippery, which has implications also for other traffic when congestion occurs. To reduce the problems it has been...

Towards an Indoor Winter Tire Classification Test

From a traffic safety perspective it is highly motivated to define winter tires interms of their performance in icy road conditions. The present definition of winter(snow) tires, introduced in the EU in 2012, is based on packed snow performance.The...

Traffic safety effects when overtaking 30 meter trucks

The purpose of this paper is to investigate if the introduction of extra-long and heavy trucks has an effect on traffic safety on Swedish roads, especially in relation to overtaking maneuvers. Traffic safety effects will be measured in terms of road...

Trafiksäkerhetseffekter vid införande av längre och tyngre fordon: en kunskapsöversikt

This review concerns potential traffic safety effects from the introduction of longer and heavier trucks than those currently allowed in Sweden. For this purpose, a summary of results from accident studies, literature summaries and in-depth studies...

Effects of forward collision warning, initial time headway and repeated scenario exposure...

To address the research questions, acritical lead vehicle braking scenario and anFCW system was developed and pilot tested in Saab’s fixed based driving simulator in Trollhättan. After piloting, the scenario was implemented in VTI’s moving base...

Final testing protocols

This report is the final document summarizing the inspection and testing protocols of the eVALUE project. It describes principles, inspection protocols and testing protocols for performance testing of ICT-based safety systems. The inspection...

Prediction of flow rutting in asphalt concrete layers

This paper evaluates an approach for predicting rut formation in asphalt concrete (AC) layers. The approach is based on a linear viscoelastic model for predicting permanent vertical strain in AC layers subjected to a moving load. The input data are...

Tema miljörisker: miljörisker och trafikanters beteenden

This report compiles the results from the project Theme Environmental risks. More specifically, the project concerned how different transport related environmental risks influence different road users and how their behaviour influence the...

The importance of tyre grip for the ESC function on icy roads

In this study we have investigated how tyres with different road grip affect the stability of passenger cars equipped with Electronic Stability Control (ESC) systems during winter road conditions. A field test with a double lane change manoeuvre on...

Trafiksäkerhetspåverkan vid omkörning av 30-metersfordon

The Swedish Road Administration considers permitting longer and heavier trucks on Swedish roads, provided that they do not affect traffic safety. The purpose of the study was to investigate the effect of truck length, particularly accident risk...

Överstyrning på is och snö med olika vinterdäck: metodutveckling och fältstudie

Traffic accidents during winter time are to a larger extent categorized by loss of vehicle control resulting in a skidding accident, compared to accidents occurring summer time. In a study by the Swedish Transport Administration, it was shown that...

Bus accidents in wintertime

Buses in Sweden have a low accident risk. However, statistics from 1996 - 2002 indicate that the number of bus accidents in Sweden with personal injuries have been increasing by 4% yearly. Buses also have a higher percentage of accidents that occur...

Handling of buses on slippery roads during the influence of side wind: A study of the...

Accident statistics assembled by the Swedish National Road and Transport Research Institute (VTI) have shown that buses are overrepresented when it comes to accidents on icy and snowy roads. For a better understanding of the problem, the performance...

SHAKE - an approach for realistic simulation of rough roads in a moving base driving...

With today’s advanced measurement equipment for measuring roads, it is possible to measure road geometry at high precision within a large span of wavelengths. Detailed information about the roads longitudinal and lateral profile, including macro...

A test method for evaluating safety aspects of ESC equipped passenger cars: a prototype...

Active safety systems are becoming increasingly common in today's vehicles. Electronic Stability Control (ESC) systems were introduced during the end of the 1990s, and accident statistics show that they have had a huge impact on traffic safety. In...

Effekter av vinterdäck: en kunskapsöversikt

Choice of winter tyres has, from mainly being a matter of safety and economic costs for wearing of road pavements, during later years also become a matter of inhalable particles formed during pavement wear from studded tyres and their negative...