ISA Trials, Gent

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ISA Trials, Gent
General information
Type: Field operational test
Tested system/service: Intelligent Speed Adaptation
Countries: Belgium 62 test users
4 partners 37 vehicles
Active from 10/2002 to 12/2003
Sven Vlassenroot
Gent University
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In October 2002 the first ISA-trial in Belgium was started in Ghent. 34 cars and 3 buses were equipped with the “active accelerator pedal (Limit Advisor M2002 from the Swedish company Imita)”. In this system a resistance in the accelerator is activated when the driver attempts to exceed the speed limit. If necessary, the driver can overrule the system. The main research goals of the trial in Ghent were to evaluate the effects of ISA on speed-change, traffic safety, drivers’ attitude, behaviour and drivers’ acceptance. To study these effects of the ISA-system both surveys and logged speed data were analyzed. In the surveys drivers noticed that the pedal assisted them well in upholding the speed limits and that the system increased driving comfort. Most important drawbacks were technical issues.

Data analysis shows a reduction in the amount of speeding due to the ISA-system. There is however still a large remaining percentage of distance speeding, especially in low speed zones. Differences between drivers are large. For some drivers speeding even increases despite activation of the system. For less frequent speeders average driving speed almost always increases and for more frequent speeders average speed tends to decrease. With the system, less frequent speeders tend to accelerate faster towards the speed limit and drive exactly at the speed limit instead of safely below, which causes average speeds to go up.

Details of Field Operational Test

Start date and duration of FOT execution

October 2002 – December 2003 (14 Months)

Geographical Coverage

The FOT took place within an area of approximately 8 x 4 sq. km in the city of Ghent, Belgium. The test area covered the city of Ghent, within the ring-road R4. All legislated speed limits (15kph, 30 kph, 50 kph, 70 kph, 90 kph) within this area were put on a digital map. Inside the test-area the system could not be switched off. Outside the test-area, the participants could choose to enter a speed limit manually to activate the system.

Link with other related Field Operational Tests

ISA-trial in Ghent was part of the European PROSPER-project.

The same ISA-system was used in the large-scale trial in Sweden. For more information, see ISA: Large-scale trials of Intelligent Speed Adaptation in Sweden.


The main research goals of the trial in Ghent were to evaluate the effects of ISA on speed-change, traffic safety, drivers’ attitude, behaviour and drivers’ acceptance. Two methodologies were used: (1) a behavioural study using questionnaires and (2) data-logging. The questionnaires were held once before driving with the AAP, during the trial (AAP active) and at the end of the trial. Data-logging was done during whole the trial.

The trial was also used to create awareness of ISA by the public: In the trial, some drivers were chosen as role-models. These drivers had a delegating and public function at the council of Ghent, institution or company and were chosen because they could make the communication in the companies about road-safety devices easier, but also they could have a certain influence in the public media, in term informing the general public, decision and opinion makers, but also the use of role-models made it easier to get involvement of the press and media.


Comparison of logged speed data during the activation period and speed data after this period showed that ISA had an effect on speeding. Effects were highest in the 90 km/h zone where speeding decreased by almost 10%. At lower speed limits effects were smaller although speeding was more frequent. In the 30 kph zone distance speeding decreased from 45.9% to 42.8%, which means that the counter pressure was overridden in a vast amount of distance. Comparing effects on a monthly basis showed a higher amount of speeding at the end of the activation period than at the beginning. Especially in low speed zones speeding increased during the first months of usage. Differences between drivers were however large. Distance speeding with the system varied between 3% and 50%. For most drivers speeding reduced with the system. Average speed of less frequent speeders tended to increase as drivers accelerated faster to the speed limit and drove exactly at the speed limit in stead of safely below. Average speed of more frequent speeders tended to decrease. The aggregated speed effects even indicated that drivers with the AAP will drive closer towards the speed limit.

When questioning basic attitudes in the surveys, most of the drivers did not think that driving fast is fun, liberating or exciting, before, during or after the project. Most drivers declared that speeding is dangerous, reckless and not sportive. Driving with ISA changed their behaviour on speeding: during the project, most of the drivers declared that they never drove faster on highways, outside urban areas, in urban areas and 30-zones. The drivers used the system voluntary on highways and outside urban areas, which gave a first indication of their acceptance of the active accelerator pedal. They also experienced the pedal as satisfying and useful. After the trial, the private test-drivers could choose to keep the ISA-system in their car. 15 private car holders chose to keep the system in the vehicle after the test-period, which was a significant indication that there is an acceptance of the active accelerator pedal. The drivers noticed that the system assisted them well in upholding the speed limits and provided for comfortable and relaxed driving, although certain technical issues could be better.

The drivers’ perception on the effect of the system was evaluated more significant than the results from the logged speed data. Data logging problems could have influenced these results. The logged data were fully analyzed without making any distinction in road-characteristics. In this trial, the logged data was analyzed in total. In similar trials only stretches of roads were examined. The benefits are here that the research environment is controlled. Total analyses, like in this trial, make it possible to have a full picture of all the driving behaviour in the test-area. Although the drivers declared that ISA is most useful in lower speed-areas, observed driving behaviour showed the opposite. It is assumed that different factors could have influenced the drivers. It is considered that factors, also described by Parker (1992), Brown (2002) and Levelt (1998), like driving behaviour of other (non-ISA) drivers and discrepancy between the design of the road and the speed limit encouraged the test drivers to speed. These effects were not measured, but reports of some drivers could acknowledge this. Also these factors will not fully explain the speeding in lower kph zones.

As noted the less change in perception of their speeding behaviour in the questionnaires, the experience of ‘driving slow’ and the logged data could indicate that there is less acceptance of the 30 kph speed limit, although they also had declared to understand the benefits towards road safety of lower speed area. This effect of non-adaptation when even speed warning devices are used could be seen as disturbing for road safety measures. Lower speed limits like 30 kph (areas) are assumed to harmonise motorised with non-motorised traffic on an acceptable and safe manor in the benefit of all road users. Mostly this would indicate road infrastructure measures to support visualisation for the road users, limitation of passing motorised traffic, etc. (Broeckaert, De Mol, 2004). A lack of tradition, less sensitization and the sporadic coherence in implementation of lower speed areas led also to a general modest acceptance of 30 kph areas in Belgium. The driving behaviour of the ISA test-drivers must be placed in this context, certainly because during the project the 30 kph areas in Ghent increased significant. These results about the speeding behaviour must not be seen as indications about ‘the failure’ of 30 kph areas, but should be noted to give an impulse into future research about implementation, visualisation and acceptance of embedded speed limits.

As a final conclusion it can be noted that ISA can have benefits in road safety and could even open new debates about speed policies. In this trial ISA could be seen as a supportive system in road safety, but can not be seen as the only manner to reduce speed violation. The use of ISA must also be geared to other road safety policies in reducing speed: better understanding of speed areas by drivers and better embedding of speed limits in relation with the use of the road should be considered.

Lessons learned

What should be improved in the Limit Advisor M2002 for future trials?

• Increase limiter's overall lifetime through higher mechanical reliability

• Use standard geographical coordinates (WGS84 for example)

• Use differential GPS for a better positioning accuracy

• Use a common sensitivity of the odometer for both the functional and the analytical sides.

• The choice of the reference speed (either actual speed or speedometer speed) and the dynamic or static type will depend of the relative importance of the technical and the human factors.

• The validity, accuracy and relative/absolute character of the existing logged data should be carefully checked, as well as the accordance with the limiter's behaviour. The active accelerator's on/off status and an evaluation of the GPS accuracy should be added to the list of logged variables.

• Improve dead reckoning hardware (gyroscope, sensors) and software

• Optimise the map-matching algorithm

• Testing other wireless communication technology (DAB, DSRC, UMTS, etc.) for digital map or logged data transmission. A static version is otherwise a stable solution.

Main events


Summary, type of funding and budget

This project was made possible with the financial cooperation of the Belgium Institute for Road Safety, the City of Ghent, the insurance company DVV, the provincial administration of Eastern Flanders, Volvo Cars and the regional public transport company "De Lijn".

Cooperation partners and contact persons

Main Contact person

Sven Vlassenroot

Coordinator and researcher during trial

Ghent University

Institute for Sustainable Mobility

Vrijdagmarkt 10/301

B -9000 Ghent


T. +32 9 331 32 59

F. +32 9 331 32 69

Sven Vlassenroot

Applications and equipment

Applications tested

Intelligent Speed Adaptation (ISA)


20 vehicles were owned by private test drivers, 17 vehicles were owned by non-private entities: 6 cars of the City of Ghent, 5 vehicles of the Ghent University, 3 buses of the regional public transport company, 2 vehicles of the Province of East-Flanders and 1 vehicle from Volvo Cars Ghent.

Equipment carried by test users


Test equipment

Active Accelerator Pedal of the company Imita, GPS Antenna, navigator, control unit (CPU), odometer, mechanical unit (servomotor regulating the accelerator's resistance), display and data logger.


Pre-simulation / Piloting of the FOT

Method for the baseline

In the period before activating the ISA-system (26 October 2002) reference measurements were carried out to analyse the driver’s behaviour in normal conditions.

Techniques for measurement and data collection

Objective data

A data logger was situated in the navigator housing. Within the digital map area, the data logger recorded 5 times per second the date and time, the position in plane coordinates, the speed, the distance, the gas pedal position, the heading, the speed limit and the RPM. Outside the map, the data logger recorded once per second the date and time, position in plane coordinates, the speed, the distance, the gas pedal position and the voluntary use of ISA by the driver.

The downloaded data were stored in a SQL-database for further analysis.

Subjective data

3 questionnaires, before, during and after the trial.

Recruitment goals and methods

Overall 62 drivers: 42 male and 20 female over different ages.

Methods for the liaison with the drivers during the FOT execution

Methods for data analysis, evaluation, synthesis and conclusions

To study behavioural effects for the Ghent trial, the following parameters were examined: average speed, standard deviation, 85 percentile speed, percentage speeding and speed distribution. All data are included to avoid the impact of the choice of locations on the results. These parameters are calculated both time-based and distance-based. A time-based calculation signifies that all logged data are weighted equally. Time-based speeds are based on average speeds at which people travel per second. This means that zero speed (0 km/h) is incorporated in the calculation of average speeds. These calculations are useful to estimate effects on travel time. Distance-based speeds are calculated based on average speeds at which people travel per metre. Idling is not incorporated in the calculation as no distance is covered and higher speeds are weighted more heavily in the calculation of averages as more distance is covered per second. A bias towards slow speeds is hereby avoided.

Sources of information

Driving with Intelligent Speed Adaptation: Final Results of the Belgian ISA-Trial

A Final Technical Report on the Belgian Intelligent Speed Adaptation (ISA) Trial