Hello, I am trying to conduct a sensitivity analysis of car-following and lane-changing parameters in SUMO for hypothetical freeway segments (basic and weaving). I tried changing headway values (car-following) and lcStrategic values (lane-changing) for a basic segment. I used lcStrategic values of 500, 1000, and 1500 for trucks in simulations (length = 15.25m). My trucks are using the CACC model. The two metrics I am interested in are the travel rates (secs/ mi) by vehicle type and the number of lane changes per vehicle type. I found that there was no change in travel rate and a number of lane changes when I changed the value of lcStrategic to 500, 1000, and 1500. I don't understand why there was no effect of changing the parameter values. Next, I want to look into other parameters like "lcLookaheadLeft", "lcAssertive" and "lcSpeedGain".
*Question*: I would like to understand the units of the parameters "lcStrategic" and "lcLookaheadLeft", "lcAssertive" and "lcSpeedGain". The SUMO documentation says: 1. lcStrategic: The eagerness for performing strategic lane changing. Higher values result in earlier lane-changing. default: 1.0, range [0-inf), -1 A value of 0 sets the lookahead-distance to 0 (vehicles can still change at the end of their lane) whereas -1 disables strategic changing completely. 2. lcLookaheadLeft: Factor for configuring the strategic lookahead distance when a change to the left is necessary (relative to right lookahead). default: 2.0, range [0-inf) 3. lcAssertive: Willingness to accept lower front and rear gaps on the target lane. The required gap is divided by this value. default: 1, range: positive reals 4. lcSpeedGain: The eagerness for performing lane changing to gain speed. Higher values result in more lane-changing. default: 1.0, range [0-inf) These definitions don't mention any units explicitly, are they all factors? i.e. unitless or are some of them in meters and some unitless? I was checking the code <https://github.com/eclipse/sumo/blob/main/src/microsim/lcmodels/MSLCM_LC2013.cpp#L1850>for LC2013 and found that look ahead distance (laDist) is being calculated as follows: laDist = myLookAheadSpeed * LOOK_FORWARD * myStrategicParam * (right ? 1 : myLookaheadLeft); If this is how the look-ahead distance for a vehicle is calculated when making lane-changing decisions, then both lcLookaheadLeft and lcStrategic specified will be used to calculate laDist but I don't know what what the units of any of these parameters are. For laDist to be in distance units, speed would be multiplied by time here. Please share any information that is available as it would help me understand my results better. Thanks, Soumya.
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