The purpose of the main roads and regional roads is to provide intra-regional connections between regional centres of economic activity and households and connections to higher road categories. Traffic between neighbouring and/or distant regional centres is supported by motorways, which are designed to bear heavier loads.
In 1998 the Road Administration set up road signs, which prohibited the usage of parallel state roads, where the motorway existed, for all heavy vehicles exceeding 7.5 tonnes. In September 2000 the Government decided to remove the ban. Avoidance of toll stations by heavy vehicles could cause significant increases in economic and financial costs for road users and road maintenance, as well as increases in the external costs of traffic (traffic safety, noise, vibrations). On the other hand avoidances are also reflected by reduced toll revenues.
The purpose of the study was to analyse the conditions on three branches of the motorway network (South West corridor - Primorska, South East corridor - Dolenjska, North East corridor - Štajerska) and on parallel regional roads as well and to evaluate the impacts of changed traffic flows caused by the abolition of the restriction on using parallel state roads for heavy vehicles. The study represents an expert-knowledge based groundwork for the analysis of this measure, paying attention also to direct and indirect impacts of the measure.
For three motorway corridors and the parallel state and regional roads the increase in road user and road rehabilitation costs and the reduced toll revenue were calculated. Also the external effects of increased traffic were quantified (emissions, noise and traffic accidents). Emissions of CO2, NOx, VOC and SO2 were evaluated.
For three motorway corridors and the parallel state and regional roads the increase in road user and road rehabilitation costs and the reduced toll revenue were calculated. Also the external effects of increased traffic were quantified (emissions, noise and traffic accidents).
On the South West corridor (Primorska) the additional increase of heavy vehicles traffic on diversionary roads bypassing motorways has been determined on the sections Ljubljana – Vrhnika (average daily increase of 88 heavy vehicles) and Postojna – Kozina (average daily increase of 180 heavy vehicles). On the Primorska corridor section Divaca – Sežana an increase in number of heavy vehicles could not be confirmed. On the South East corridor (Dolenjska) the additional avoidance is substantial. The average daily increase of trucks on the by-pass road amounts to 182 vehicles. On the North East corridor (Štajerska) the average daily increase in the number of heavy vehicles amounts to 107.
The increase of the external impacts of traffic was determined on a quantitative basis. Evaluated were the emissions of CO2, NOx, VOC and SO2. The most significant increase of emissions was found on the Dolenjska branch (more than 50%), whereas the increase on other two branches amounts to 15% on average. Furthermore, the increase of emissions on previously less loaded individual sections, is significantly higher.
The increase in noise pollution due to additional diversion of heavy vehicles from motorways to parallel state roads is relatively small. A higher level of noise pollution was found on only one road section.
According to estimations the diversion of heavy vehicles to state roads in the next 20 years could result in 3 to 5 more traffic accidents per km on bypass roads if compared to the situation with no diversion of heavy vehicles to state roads.
The results of research have shown that the driving restrictions of heavy goods vehicles on regional roads, where the parallel motorways exist, is justified. With an abolishment of this restriction the efficiency of the traffic system has worsened, the environmental emissions have increased, and the abolishment of the restriction has not been in accordance with the efforts to shift freight traffic towards rail transport.
Because of the construction of new motorway sections as well as re-routing and increase in traffic flows, it would be necessary to again analyse the existing road network and determine restrictions for heavy vehicles on those parallel regional road sections, where the diversion of heavy vehicles and all related negative impacts are significant.