limiting deceleration

[mattinjersey]

I wanted to limit the deceleration to physically reasonable values?
Is this the way to do it? Did not seem to limit the deceleration as desired.
I put it in road.js after the vehicle is created.
Thx

if (vehNew.type=="car")
{
vehNew.longModel.bmax = 5/3.6;
}
else
{
vehNew.longModel.bmax = 0.5/3.6;
}

[MTGermany]

This should work in principle. However, there are two issues

(1) Why do you divide the decelerations by 3.6? All units in my simulator are SI units (speed m/s, accelerations m/s^2), so your values are much too low. Particularly the truck value is too low. Even a rolling truck without applying any brakes will decelerate at about 0.2 m/s^2 by rolling resistance and air drag. Traffic light amber phases impose a deceleration of up to 3 m/s^2 unless you want to cross red traffic lights once in a while. Physically feasible values for cars are 9-10 m/s^2, and for trucks 5 m/s^2. Notice that bmax does not denote the regular deceleration (for this, we have the IDM parameter b) but the physical maximum in an emergency braking.

(2) I suspect that your model is overwritten by road.updateModelsOfAllVehicles(..)
in the main simulation update updateSim of the corresponding scenario distributing template models to all vehicles on the network. The reason is that the models are changed all the time by user interaction, speed limits, tactical lane changing or deceleration before off-ramps and others. So you should do the same as in the callback for changes of the model-parameter sliders: Change the relevant template models longModelCar and longModelTruck but do so after the function updateModels() is called in the initialization phase (this function is used to change the default settings in the constructor of the longitudinal model to the starting values used for the respective simulation).

You could also change bmax directly in the constructor of the ACC model (a variant of the IDM that is actually used in the simulator). This is guaranteed to work because it is nowhere overwritten. However, you will have the same value for cars and trucks (as in my simulations).

[mattinjersey]

great. As far as the factor of 3.6, it looks like a scaling factor in your code. If you search for 3.6, you will find that many of the values in your code are scaled by 3.6. I am not sure why, perhaps you could explain it.

[MTGermany]

Scaling typically applies to translate the visible speed (for example in the speed sliders) to the internal representation which is always in SI units: speed in m/s is 1/3.6*speed in km/h. For the acceleration, however, the common unit is already SI: m/s^2, so there should not be any scaling factors in the code relating to accelerations.

By the way: It is really a Golden Rule for simulations to always use SI units. Satellites have been lost causing hundreds of Million Dollars damage because the navigation system used other units as the propulsion system. So input is scaled internally to SI, the calculations are done consistently in SI, and the output is scaled back to common units such as km/h, mph or Angstroem per week ;-)