how can I set the vehicle to drive at a constant speed in sumo file? - sumo

Question

How can I set the vehicle to drive at a constant speed? I find the speed of vehicle increases firstly and then drive at speed between 14.5 and 14.7 m/s in sumo. But I want the car drive at a constant speed in sumo. What shuould I do?
helloWorld.net.xml
<net version="1.3" junctionCornerDetail="5" limitTurnSpeed="5.50" >
<location netOffset="0.00,0.00" convBoundary="-300.00,0.00,300.00,0.00" origBoundary="10000000000.00,10000000000.00,-10000000000.00,-10000000000.00" projParameter="!"/>
<edge id=":1_0" function="internal">
<lane id=":1_0_0" index="0" speed="13.89" length="0.10" shape="0.00,-1.60 0.00,-1.60"/>
</edge>
<edge id="gneE0" from="0" to="1" priority="-1">
<lane id="gneE0_0" index="0" speed="13.89" length="300.00" shape="-300.00,-1.60 0.00,-1.60"/>
</edge>
<edge id="gneE1" from="1" to="3" priority="-1">
<lane id="gneE1_0" index="0" speed="13.89" length="300.00" shape="0.00,-1.60 300.00,-1.60"/>
</edge>
<junction id="0" type="dead_end" x="-300.00" y="0.00" incLanes="" intLanes="" shape="-300.00,0.00 -300.00,-3.20"/>
<junction id="1" type="priority" x="0.00" y="0.00" incLanes="gneE0_0" intLanes=":1_0_0" shape="0.00,0.00 0.00,-3.20 0.00,0.00">
<request index="0" response="0" foes="0" cont="0"/>
</junction>
<junction id="3" type="dead_end" x="300.00" y="0.00" incLanes="gneE1_0" intLanes="" shape="300.00,-3.20 300.00,0.00"/>
<connection from="gneE0" to="gneE1" fromLane="0" toLane="0" via=":1_0_0" dir="s" state="M"/>
<connection from=":1_0" to="gneE1" fromLane="0" toLane="0" dir="s" state="M"/>
</net>
hello.rou.xml
<routes >
<route edges="gneE0 gneE1" color="yellow" id="route_0"/>
<vehicle id="vehicle_0" depart="0.00" color="red" route="route_0"/>
</routes>

Answer 1

You need to disable random dawdling by setting sigma to 0 and start with the maximum speed. To do so you need to define a vehicle type:
<routes>
<vType sigma="0" id="t1"/>
<route edges="gneE0 gneE1" color="yellow" id="route_0"/>
<vehicle id="vehicle_0" depart="0.00" color="red" route="route_0" departSpeed="max" type="t1"/>
</routes>