**3.1 The impact of loading on track maintenance**

In order to highlight the main difference between treating track loading as grosstonnage or as specific damage for different track components, this paper delivers results based on an artificial network. Note, this network is also used in [1] dealing with the impact of different track-related boundary conditions on overall track maintenance and renewal. We add the line speed as a parameter and use the modulation done in [1] concerning superstructure components.

The network covers 10,000 km with a given radii distribution and line speed distribution for the straight sections given in **Table 6**. To keep the focus on the loading, we model the maintenance for a given, constant track consisting of heavy superstructure (concrete sleepers, wooden sleepers in the sharp curves R ≤ 250 m 60E1-R260 rails) on medium ballast quality, good subsoil and good drainage condition. The tracks are loaded with 30,000 gross-tons per day everywhere in the network. Both assumptions are never true for any existing network, but were chosen for illustration purposes.

According to the track maintenance assessment provided by [1], this network characteristics deliver a certain track maintenance and renewal demand depicted in **Table 7**.

For applying the alternative description of track loading proposed in Section 2, we need to have a closer look at the transport load. The traffic mix shows long-distance passenger trains (LDP), regional passenger trains (RP) and freight trains (F) consisting of different vehicles (**Table 8**).

The train configuration of the different market segments is depicted in **Table 9**. The long-distance train is a loco-wagon train with a maximum speed of 160 kmph (and thus reaching the maximum line speed). For the regional passenger traffic, the traffic mix consists of two different types of electric multiple units (EMU), one (EMU1) with a total weight of 160 tons consists of four powered bogies and two trailer bogies (axle scheme Bo'Bo'2'2'Bo'Bo'), the other one (EMU2) is a lighter and shorter trainset with two powered bogies and three trailer bogies (axle scheme


#### **Table 6.** *Reference network.*


#### **Table 7.**

*Maintenance and renewal demand for the reference network.*


#### **Table 8.**

*Traffic mix.*


#### **Table 9.**

*Train configuration.*

Bo'2'2'2'Bo') and a total weight of 127 tons. The freight trains are modeled as some 1000 ton-trains with one four-axle loco and a mix of empty, medium-loaded and fullloaded freight wagons (detailed loads see **Table 9**), all with two Y25-bogies.

#### *3.1.1 Ballast maintenance*

The transport volume for the entire network can be addressed as gross-ton-kilometers or as damage-kilometer following Section 2. For the latter, for the ballast maintenance we need to calculate the P2-forces, specifically for the different line speed sections. Thereby it is to be considered that the train speed may be limited by the allowed maximum vehicle speed and not by the given line speed. For freight trains, the maximum speed assessed for this calculation is 100 kmph. Thus, for all sections with higher line speeds the damage increments D1 (P2-force) are calculated with 100 kmph only. What we can see directly from **Table 10** is that the alternative description of "loading" moves relative damage shares toward long-distance passenger traffic. This effect is mainly driven by the higher speed as axle loads for these two traffic segments are about the same on average. The share of regional passenger traffic remains almost the same as speeds are higher than in freight transportation, but axle loads lower.

We know that this loading leads to 1747 kilometers of necessary tamping in the network or a tamping interval of 5.7 years (6 years in the straight sections). If we allocate this tamping demand to the loading, we can calculate an incremental tamping demand for the unit gross-ton-km and the alternative unit kN<sup>3</sup> km.


#### **Table 10.**

*Track loading.*

