Erik Nuyts - Academia.edu (original) (raw)

Papers by Erik Nuyts

2008 TRB National …, 2008

Abstract: Roundabouts in general have a favourable effect on traffic safety, at least for crashes... more Abstract: Roundabouts in general have a favourable effect on traffic safety, at least for crashes causing injuries. Especially the number of severe crashes (fatalities and crashes involving serious injuries) appears to decrease after converting intersections into ...

Urban Planning

This article introduces a method for advancing environmental and social sustainability objectives... more This article introduces a method for advancing environmental and social sustainability objectives in relation to home renovations laid out in European and Belgian policies. The comfort tool is an instrument that simultaneously addresses the energy efficiency and universal design aspects of a sustainable home renovation while being usable and meaningful to laymen homeowners and improving their communication with building professionals. It is based on recent research exploring a synergetic merging of energy efficiency and universal design in housing through the concept of indoor environmental comfort. It employs comfort as a way of intervening in the decision-making process for energy efficiency and universal design measures in home renovations. The comfort tool takes a user-centered approach and rests on an interdisciplinary set of theoretical constructs bringing together knowledge from psychology, nursing, design, and building sciences. Besides describing the method itself, the arti...

Human Physiology, Sep 1, 2021

This report discusses the effect on traffic safety of overtaking restrictions for trucks on motor... more This report discusses the effect on traffic safety of overtaking restrictions for trucks on motorways. For this purpose, literature is reviewed and Flemish data are analyzed. The international literature does not allow a univocal conclusion. As an effect of the overtaking restriction for trucks, speed of trucks decreases, but speeds of the cars and of the traffic as a whole can increase or decrease. Also spacing can increase or decrease. Often homogeneity of the global traffic flow increases. But also the number of overtaking by private cars increases as does the speed variance between cars and trucks. To what extend these different effects counterbalance one another, is not evident. The effect of overtaking restrictions on the number differs between study sites: both an increase and a decrease of accident numbers have been reported. Only one study found one significant result, being a decrease of the number of accidents. A second purpose of this study was to calculate the effect of the restriction of overtaking by trucks on the number of accidents on Flemish motorways. The effect is calculated with the method presented by Hauer (1997). This method corrects both for the general accident trend on Flemish motorways and for regression to the mean. This correction is based on the use of a comparison group. The number of accidents of this comparison group was calculated using an accident risk model, that has been worked out especially for the present study. The model is based on all the injury accidents of the Flemish highways that happened between 6-10h and 16-19u. Since it is possible that the restriction of overtaking for trucks also influences the number of accidents in which no trucks were directly involved (e.g. by improving homogeneity of the global traffic flow) all injury accidents are considered in the analyses. Possible problems with the overdispersion factor are accounted for by a sensitivity analysis of the dispersion factor. The calculated results have a major disadvantage. The after period contains only one year. As a consequence, the number of accidents in the after period is limited. Moreover, chance influences the results more than could be hoped for, since an occasional extreme result is not been blunted by data of a second year. Hence, the results have to be interpreted with care. In general, we can conclude that the impact of the measure depends strongly on the location. On the link segments of only one location we find a statistically significant decrease of the number of accidents with 82%. On the entry zones of two locations a statistically significant decrease of the number of accidents with 78-82% is found. On the 42 other segments no significant results have been found. In the most extreme cases, the number of injury accidents is found to decrease with 85% or to increase with 175%. In most cases, the confidence interval of the estimate of the effect was that large, that increases nor decreases were statistically significant. Using meta-analysis the results of several locations can be taken together. Although none of the accident increases in itself was significant, the increases dominate in the meta-analysis. Meta-analysis of the link zones results in a statistically significant increase of the number of accidents with 36%. Meta-analysis of the entry zones gives a statistically significant increase of the number of accidents with 47%. For the exit zones, the dispersion factor could not be found during the modelling process. A sensitivity analysis of the dispersion factor resulted in accident increases ranging from 30% to 63%. The largest increases were statistically significant. It is concluded that the impact of the overtaking restriction for trucks on motorways depends strongly on the specific location. Apart from the restriction as such, other factors influence the impact on traffic safety. These factors could be infrastructural, but also not yet identified human or environmental factors. In a limited number of locations a positive result is found, but the meta-analysis does not at all support the idea that the measure increases traffic safety. Based on the present results, abolition of the measure is not recommended for those places where there was a positive effect. Further research should show under which conditions the measure has a positive impact on traffic safety. But the after period of the present study is short, only one year. This limits the generality of the results. Yet, from the present results and the review of the international literature, it can be concluded that overtaking restriction for trucks on motorways is a measure that should be handled with care. Depending on the location, the number of accidents can decrease or increase. And since in the meta-analysis the effect of the measure is negative, general introduction is not recommended. When sufficient data are available, the present study should be extended. New data can raise the number of segments with an…

The safety of school children in traffic in Flanders is a major problem. The majority of accident... more The safety of school children in traffic in Flanders is a major problem. The majority of accidents involving children take place when school starts or ends. In order to make the close vicinity of schools safer, in 2004 the Belgian government decided to lower the speed limit in every school zone to 30 km/h. This can be done with permanent signs, or with variable message signs only operating at school starting and ending hours. The aim of this measure is to lower the speed of passing cars, supposedly lowering the number of accidents and the severity of accidents in this area. This measure became effective on September, 1st 2005. This report describes the results of a case study that examines the changes in the speed profile at 11 school zones where this measure was taken. The type of signalisation was taken into account, as well as the surroundings of the school entrance. The effects on mean speed were calculated as well as for the whole day as for relevant moments like the start of school. This calculation was done with a comparison group where available, to correct for the general trend in traffic safety. Effects were calculated few months after the measure was taken and several months later. Changing the speed limit from 50 km/h to a permanent 30 km/h, lowered the mean speed and V85. In school zones with a low mean speed before the measure was taken, the mean speed didn't change much. A permanent 30 km/h zone at two schools on a road segment with a speed limit of 70 km/h, lowered the mean speed and the V85 in the first months, but after a few months, the mean speed in one zone was back at the same level before the measure was taken. A variable 30 km/h zone with variable message signs, indicating the lower speed limit only when school starts or ends, was installed in 2 school zones where the speed limit was 50 km/h. This measure lowered the mean speed during the day only minimally, and the change in mean speed at the start of school is even smaller. A variable 30 km/h zone on a 70 km/h road segment, resulted in a clear decrease in V85 speed at the start and the end of school hours, as well as the V85 of the whole day. It was found that the effect of the type of 30 km/h zone depends on the situation before the measure was taken. A permanent 30 km/h zone has the most effect on a 50 km/h road segment, while the biggest effect of a variable zone is found on a 70 km/h road segment. Locations where the vicinity of the school clearly indicated the function of the road showed a lower mean speed during the day as well as during the night. On locations where the function of the road wasn't visible, the mean speed at night didn't change much. Decision trees used by the road authorities during the decision of the type of 30 km/h zone in a certain school area, take into account the function of the road (residential or flow/connecting road) and the existing speed limit. However, in these decision trees, more attention could be paid to the readability of road and the school environment to indicate the function of the road. 1 to 3 months after installation of a 30 km/h zone on a 50 km/h road segment, this measure results in a significant decrease of -5,7 km/h in the daily mean speed, and a significant decrease of -5 km/h between 8AM and 9AM. These figures were corrected for the general trend in road safety by means of a comparison group. More than 4 months after installation, the daily mean speed decreased significantly by -6,8 km/h, and the mean speed between 8AM and 9AM decreased by -8,6 km/h (both results without correction for the general trend). In the school zone with a 70 km/h speed limit where a permanent 30 km/h zone was installed, the daily mean speed decreased significantly few months after installation by -20,3 km/h. The mean speed between 8AM and 9AM decreased significantly by -24,8 km/h. These figures were corrected for the general trend in traffic safety. Some months later, this effect lowered: the daily mean speed had decreased significantly by -4,3 km/h, the hourly mean speed decreased significantly between 8AM and 9AM by -3,6 km/h (both results without correction for the general trend). It is found that the effect of a 30 km/h zone depends on the type of zone (permanent or variable), the initial situation and the surroundings of the school. The speed limit outside the school zone and the environment give the driver information about the function of the road, and thus influences the speed behaviour of the driver. This has to be kept in mind when deciding which type of school zone should be installed. A permanent 30 km/h zone suggests a residential function, so the environment should reflect this function in order to maximise the effect of the installed 30 km/u zone. A variable zone rather suggests a flow or a connecting function, resulting in a smaller effect when installed in a residential area. When the desired function of the road is not reflected by the current infrastructure and the organisation of…

Energy and Buildings, Aug 1, 2023

Healthier people, cleaner air and less congestion. That’s why Flemish authorities stimulate a mod... more Healthier people, cleaner air and less congestion. That’s why Flemish authorities stimulate a modal shift from cars to bicycles or public transportation. Not every car trip however can be replaced by a bicycle trip. Using the data of the Flemish Travel Behaviour Survey, it was investigated how many car trips could be substituted, taking several limitations into account. It is assumed that following trips are not substitutable to bike trips: (i) trips within a travel chain, of which another trip is not substitutable; (ii) trips of more than 5 km; (iii) home-location-home trips with staying time at the location to short compared with distance; (iv) 40% of the shopping trips ; (v) 50% of trips meant to bring someone or to pick him up again; (vi) trips of older persons; (vii) night trips of older men; (viii) night trips of women. A sensitivity analysis is performed on the results, in order to see how much the results depend on the different assumptions. The first 3 assumptions (i) tot (iii), lead to the result that 25% of all car trips are bikeable. When also the other limitations are taken into account, 17% of the trips are still substitutable, ranging from 12% to 21%. Since only the shortest trips are substitutable to bike, the percentage of kilometres travelled by bicycle instead of by car is lower (2-4%). Often, it is put forward as a general statement that modal shift from all car trips shorter than 5 km should be possible. But due to the other limitations, and especially the fact that if one trip of a chain is not substitutable, all the other trips are also not substitutable, it is found that for only 31% (range: 25% - 40%) of these short car trips modal shift to bicycle is possible.

IOP Conference Series: Earth and Environmental Science, 2020

The building stock being a huge energy consumer, is an important sector for SDG 11 on sustainable... more The building stock being a huge energy consumer, is an important sector for SDG 11 on sustainable cities and SDG 13 on climate action. Therefore, retrofitting the existing buildings is a priority for most EU countries. Long term goals for the energy performance of buildings are premised. However, to be able to monitor the progress and feasibility to achieve the goals in 2050, knowledge of the actual renovation rate is indispensable. Since years an overall renovation rate of 1% for the EU is communicated. This number is withheld in several countries to stimulate retrofitting (Belgium, Italy, The Netherlands). However, it is not clear how this renovation rate reflects the actual renovation rate and the actual energy savings because accurate knowledge on this is lacking in most countries. This paper focusses on elaborating our knowledge of the renovation rate by analysing its definition and providing a possible, more accurate calculation method. A literature study shows that there is n...

IOP Conference Series: Earth and Environmental Science, 2019

In order to achieve a sustainable built environment by 2050, the European building stock needs to... more In order to achieve a sustainable built environment by 2050, the European building stock needs to be retrofitted. Also in Belgium, with 75% of the residential buildings built before 1980, deep energy renovation is stimulated. The Flemish government premises long term goals for the energy performance of the existing building stock in the Renovation Pact (2014). To be able to monitor the progress and effectiveness of the Renovation Pact, knowledge of the actual renovation rate is indispensable. Since years, a renovation rate of 0.7% to 1% is communicated as an argument that renovation should be stimulated. However, there is little empirical evidence for this figure and how it reflects the actual energy renovation activity. Furthermore, non-energy renovation activities are considered as possible gate for home owners towards energy renovation, but little is known about these renovation activities. Since 2013, a yearly survey is done by Essencia Marketing, a marketing agency specialized ...