Segments

The segment.csv files defines the road segments that make up the network. The segments are directionally oriented and have a starting and ending node, which must match to a node in the vertices.csv file (see vertices). Other data values in the segment file describe the length of the line segment (in map units) and road cost information. See the Table 19, “Segments file format description” for a description of the segment file format.

Table 19. Segments file format description

Field nameData typeDescription
SEGMENTStringA unique, arbitrary alphanumeric label that is used to identify the segment for matching purposes. The label should not contain special characters or spaces.
FNODEStringAn alphanumeric label used to identify the node at the beginning of the road segment. The node must exist in the vertices.csv file.
TNODEStringAn alphanumeric label used to identify the node at the end of the road segment. The node must exist in the vertices.csv file.
RDTYPEStringAn optional label used to classify the type of road segment. This field is used for descriptive purposes only.
LENGTHFloatThe length of the road segment in map units.
MAINTAINFloatThe cost to keep the road segment open for use in a planning period ($). If the road segment is used to transport any amount of product during a planning period this value will be added to the road maintenance account. If the road segment is not used this value will not be charged.
BUILDFloatThe cost to 'construct' the road segment the first time that is used ($). The first time the road segment is used to transport any amount of product during a planning period this value will be added to the road construction account. During subsequent planning periods the construction cost is not charged. If the road segment is never used this value will not be charged.
HAULFloatThe cost to haul wood across the road segment during each planning period ($/unit product). The amount of wood transported across the road segment will be multiplied by the hauling cost and added in to the appropriate hauling account.
DIRECTIONInteger

An indicator of the direction that the road is allowed to be used in.

  • 1 - the road may only be used in a forward direction

  • 2 - the road may only be used in a backwards direction

  • 3 - the road may only be used in both directions


FNODE and TNODE refers to the node identification labels described in the vertex.csv file. These end point nodes provide a rough approximation of the location of the line segment.

[Note]Note

When you implement a road model you must load up the core road files, and you can optionally load the road shape file. If you load the road shape file, then the Map Viewer will use the shapes from the shapefile to draw the roads. If you do not load the shapefile, then the Map Viewer will draw the roads as straight lines between the starting and ending vertices. This means that the original road may be windy and curved in reality, but displayed as a straight line in the Map Viewer . Regardless of whether you use the shapefile or not, all of the cost, direction and length data are read from the core files. If you do load the shapefile, then the additional attributes from the shapefile will be present in the route and network tables.

The MAINTAIN field is defined as the cost per planning period ($/period) to maintain the segment of road. The maintenance charge is assumed to cover the costs of keeping the road open (grading, culvert repair, snow plowing).

MAINTAIN costs are accrued during periods when the model selects to use the segment to transport wood. The value is a periodic cost, and is summed into the appropriate road maintenance account. If the segment is not being used to transport wood within a planning period, no maintenance charge applies.

BUILD is the one-time cost incurred to build the segment of road. This cost will only be incurred when it is necessary to use a line segment that has not previously been used (e.g. formerly inaccessible blocks accessed for the first time). After the segment is built no further building charges apply (although maintenance costs will accumulate during periods when the road is being used). If the line segment represents an existing road it should have a build value of 0. Values for road construction costs are determined in the data preparation process (i.e. using DEM's to calibrate construction cost based on terrain, adding culvert charges when corssing streams). The cost represents the fee for the entire length of the road segment.

The HAUL field contains the cost (expressed as $/unit product) to haul one unit of product over the length of the segment. This value will be multiplied by the cumulative product volume travelling over the segment on its way to a selected destination. This flexible data structure allows for reasonable hauling cost predictions to be derived from what harvest is forecast and transported on specific routes. This modelling structure correctly tallies the cumulative volume flow when tertiary and secondary segments passing volume merge on their way to the destination node.

Products can flow through the road network in a variety of ways. It is even possible for loaded trucks to pass each other carrying different products to different destinations. The DIRECTION field specifies the direction of travel allowed on the road segment (see Figure 183, “Multiple direction road segment”). A value of '1' means that products may flow from FNODE to TNODE, a value of '2' means the opposite direction, and a value of '3' means that flows are allowed in either direction. Multiple records can be added for each pair vertices. A pair of opposite direction one-way records might record differential hauling costs (cheaper to haul downhill than uphill).

Figure 183. Multiple direction road segment

If the DIRECTION value allows, products may travel in opposite directions across a road segment. In this example product A travels in a forward direction across segment 5 to mill A, and product B travels across segment 5 in the opposite direction to mill B.


The following example illustrates a number of segments.csv records.

  SEGMENT,FNODE,TNODE,LENGTH,MAINTAIN,BUILD,HAUL,DIRECTION
  0,52,68,214.375,428.75,1286.25,0.01792818,3
  1,66,68,23.82521,47.65042,0.0,0.001992502,3
  2,60,69,17.46425,34.9285,0.0,0.001460535,3
  3,67,70,43.41659,86.83318,0.0,0.003630929,3
  4,55,71,37.11992,74.23983,0.0,0.003104338,3
  5,21,72,272.125,544.25,1632.75,0.02275781,3
  6,58,72,76.37751,152.755,0.0,0.006387451,3
  7,56,73,81.86169,163.7234,0.0,0.006846094,3
  8,62,74,131.6742,263.3485,0.0,0.01101192,3
  9,46,74,291.25,582.5,1747.5,0.02435724,3
  10,47,75,300.625,601.25,1803.75,0.02514127,3
  ....