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Short Term Effects of the 1991 Scheme

The evaluations based on 1990 and 1992 travel survey data and traffic counts, concluded that over the week as a whole, there was a small decrease in total car traffic crossing the toll ring in the inbound direction. However, this decrease was smaller than the general reduction in car traffic in Trondheim during the same period. It should be noted that the early nineties was a recession period in the Norwegian economy. For a number of years there was no increase in car ownership, and in general zero growth in traffic on the roads.

Looking at time periods, inbound car traffic through the toll cordon decreased by 10% during both the high and low charged periods, and this decrease was almost offset by an 8-9 % increase in inbound car traffic during uncharged periods at evenings and at weekends. Thus, the toll ring caused a general shift in timing for car trips away from the charged hours, but the percentage reduction was not affected by the differentiation between peak and off-peak charges. 

The following table shows that for some trip purposes, adjustments were more substantial. The change in departure time was largest for home-based shopping trips, with a major increase in the number of trips outside the charged periods. Also for trips from work to home, the motorists adjusted their time of travel according to the charging system.

The travel surveys show that the number of CBD shopping trips increased in toll-free periods and decreased in tolled periods. No significant changes in destinations for shopping trips were detected. The travel surveys indicate a slight increase in the use of public transport and cycling. However, the toll ring effects are difficult to single out because of parallel improvements in public transport and in the bicycle road network. More car sharing was not detected as a response to the charging.

Measured Effects after Termination of Charging

When charging was discontinued at the end of 2005, the vehicle counting equipment at all stations was maintained in operation for at least three months. Automatic counting was kept running for six months at five stations, and for the whole of 2006 at only one of the closed stations. This enabled traffic changes between 2005, the last year with tolling, and 2006, the first year without tolling, to be studied hour by hour and day by day. 

A result for typical local traffic is shown in figure below for three stations located along the main bypass road. Whilst traffic in the formerly charged periods increased by 11.5 %, traffic for the whole week increased by only 3.8 %, and traffic at working day evenings and at weekends decreased. The total increase for working days constituted 7.5 %.

Looking at percentage of traffic within charged hours for working days, this increased to 76.5 % in 2006 from 73.9 % in 2005. This shows that motorists that were priced out during charging periods have returned back to the more preferred periods for making trips.

The following figure provides evidence that some drivers in 2005 started early to avoid being charged; traffic in 2006 between 05:00 and 06:00 decreased by 11 % whilst traffic between 06:00 and 07:00 increased by 11 %. In the afternoon, shifts in departure times to avoid being charged are even more evident; the last of the charged hours, between 17:00 and 18:00, has a 20 % increase in 2006, and an 8 % decrease in the following hour.

Finally, the next figure shows that increases in volumes for working days were largest in the afternoon, smaller during the middle of the day and smallest in the morning. This pattern may at first glance seem surprising, considering that charges were higher in the morning hours 06-10 than later in the day.

The explanation for this has to a large degree to do with how trip purposes are distributed in time during an average working day. Work, school and business trips are fairly inelastic with respect to departure time compared to other trip purposes. The split between these two groups of purposes are depicted for time intervals in the figure below, for the same origin-destination segment as in the previous figure. For the part of the day that was charged during 2005, there is clearly a negative correlation between the shift in volumes in time periods and the share of work, school and business trips in the same time periods. The larger are the share of other trips, the larger are the changes in volumes. This indicates that the progressively larger increases throughout the day can be explained by a corresponding larger share of private trip purposes, having a larger elasticity of demand with respect to the choice of departure time.

Traffic entering the city from the east is affected by the fact that the Ranheim toll plaza is still in operation. This is a bi-directional charging station in operation 24 hours a day and 7 days a week with the purpose of providing revenues for the E6 East motorway project. When the municipal charging stations were demolished, motorists in 2006 were able to make detours using routes that were now free of charge, to avoid passing through Ranheim. The result was considerable increases between 2005 and 2006 at places like Skovgård (48 % for charged periods and 25 % for average daily traffic) and Tunga (20 % for charged periods and 16 % for average daily traffic), and corresponding decreases at Ranheim (-17 % for charged periods and – 11 % for average daily traffic).

Some of the stations that came into operation close to the city centre during the last expansion of the charging system were also affected by route change adjustments. Considerable increases in traffic levels at these stations in 2006 indicate that motorists returned back to preferred routes which they had been priced out from using.

On the whole, traffic in the formerly charged periods Monday to Friday 06:00 to 18:00 increased much more than traffic during other periods of the week between 2005 and 2006. For most parts of the municipality, traffic increases for the week as a whole was in line with the general traffic growth in the county. For the southern part of the municipality, it can be argued that the annulment of charging lead to traffic increases that were higher than otherwise expected.

There has been no comprehensive study to evaluate the environmental effects of the Trondheim tolling schemes. A measuring station collecting data on PM10 dust particleswas in operation in one of the heavily trafficked main approach roads to the city centre since 1993 for the extended winter season (Oct/Nov – May/June). Due to the widespread use of studded tires and the weather conditions in the winter time, this period is the most interesting period to look at for air pollution effects. Dry and cold weather tends to bring the concentrations up to high levels.

Based on observations of PM10 levels, it is not possible to conclude that the toll ring had an effect on air quality. The variation in concentration is most likely a result of changing weather conditions.