Representing overlapping polylines in QGIS

Question

I have several shapefiles representing bus lines with different colors for each segment, however, because the lines are exactly superposed, only the shapefile on top can be seen. Is there a way to display the lines underneath for example side-by-side on these parts of segments where several lines converge (there might be 4 or 5 of them)? The polylines are made up of series of segments.

I know there are some tools in ArcGIS, but I'm using QGIS 2.8.0

Answer 1

In QGIS 2.8.0 you can do that with the offset option in the Style Layer Properties. In my example with three polylines (they are exactly superposed too):

Click in "Simple line" of line2 to display "Offset" option (I set 1 mm):

Click in "Simple line" of line5 to display "Offset" option (I set -1 mm):

The result obtained (Offset of line4 unchanged; 0 mm):

Editing note (answering to alpha-beta-soup comment):

With the next code, executed in the Python Console of QGIS, I have the same result:

from PyQt4.QtGui import *

mc=iface.mapCanvas()

layers=[]
renderer = []

n = mc.layerCount()

symbol = range(n)

symbol[0] = QgsLineSymbolV2.createSimple({'color':'green',
                                       'width':'1',
                                       'offset':'1.0'})

symbol[1] = QgsLineSymbolV2.createSimple({'color':'red',
                                       'width':'1',
                                       'offset':'0.0'})

symbol[2] = QgsLineSymbolV2.createSimple({'color':'blue',
                                       'width':'1',
                                       'offset':'-1.0'})


for i in range(n):
    layers.append(mc.layer(i))

for layer in layers:
    renderer.append(layer.rendererV2())

for i in range(n):
    renderer[i].setSymbol(symbol[i])

iface.mapCanvas().refresh()

for layer in layers:
    iface.legendInterface().refreshLayerSymbology(layer)