I've had crashes like this several times. I couldn't reproduce them, but it happened while manually driving over a Stop sign.

Error while running event PavementDriveAssist::on_tick (ID 0)
__PavementDriveAssist__/pda.lua:1179: attempt to compare number with nil
stack traceback:
    __PavementDriveAssist__/pda.lua:1179: in function 'on_tick'
    __PavementDriveAssist__/control.lua:83: in function <__PavementDriveAssist__/control.lua:82>

Also, in the Controls menu, you have an untranslated key for the custom-input:

Unknown key: "controls.set_cruise_control_limit_ok"

+1
I have a test map where I design my blueprints and test behaviors, rates, etc. I tested it with the Hauler from AAI Hauler but and had the same crash so I made a small O track to test and understand how it works and what I can create.
Made a circular track, placed the Stop sign and works every time with the three vehicles, tank, car and hauler so far. I will try to find the pattern and reproduce the error

Test 1:
Vehicle: Car
Fuel: Solid fuel
start from boxes, had stop sign half way, stopped at sign, continue riding, had a limit speed set to 20 in boxes entrance, crash at limit sign:

The mod Pavement Drive Assist (2.2.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PavementDriveAssist::on_tick (ID 0)
PavementDriveAssist/pda.lua:1179: attempt to compare number with nil
stack traceback:
PavementDriveAssist/pda.lua:1179: in function 'on_tick'
PavementDriveAssist/control.lua:83: in function <PavementDriveAssist/control.lua:82>

Repeated test removing stop sign, limit sign genrated the crash
The mod Pavement Drive Assist (2.2.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PavementDriveAssist::on_tick (ID 0)
PavementDriveAssist/pda.lua:1179: attempt to compare number with nil
stack traceback:
PavementDriveAssist/pda.lua:1179: in function 'on_tick'
PavementDriveAssist/control.lua:83: in function <PavementDriveAssist/control.lua:82>

Removed the signal from the Limit sign, vehicle pass run with no change, no error
Added a random output (purple science = 1)

The mod Pavement Drive Assist (2.2.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PavementDriveAssist::on_tick (ID 0)
PavementDriveAssist/pda.lua:1179: attempt to compare number with nil
stack traceback:
PavementDriveAssist/pda.lua:1179: in function 'on_tick'
PavementDriveAssist/control.lua:83: in function <PavementDriveAssist/control.lua:82>

I think I got it. If the Road sensor is set C = -1 or C = 0 and the vehicle pass over it and then a speed limit sign, it crashes.
With C = 1 it wont crash, wont limit speed either (not sure if should, I thought it would)

It must be related to the parameters that alter the car propertties

Circular road with this in order:
Car reset (pick up and placed again)
Stop sign
Road sensor
Speed limit signt

Scenario 1
Start circuit, reach stop sign
Car stopped
accelerate again, pass over road sensor (default values V=0, C=-1,S=0, L=60
reach limit sign, crash

Scenario 2
Start circuit, reach stop sign
Car stopped
accelerate again, pass over road sensor (values V=0, C= 0,S=0, L=60)
reach limit sign, crash

Scenario 3
Start circuit, reach stop sign
Car stopped
accelerate again, pass over road sensor (values V=0, C= 1,S=0, L=60)
reach limit sign, pass with no speed alteration (over speed limit)

Another thing I detected: If the car is stopped by the stop sign or because it went off road (stopped by the mod, not the player) AND then i change C=0 the car starts accelerating by its own. If the car is stopped by the player this will have no effect.
I removed the limit sign, changed C=0 and the car started accelerating, going in circles in the track. After 2 laps I decided to change C=0 and 1 so see it stop and move again on its own. I changed it to -1 and crashed
The mod Pavement Drive Assist (2.2.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PavementDriveAssist::on_tick (ID 0)
PavementDriveAssist/pda.lua:1179: attempt to compare number with nil
stack traceback:
PavementDriveAssist/pda.lua:1179: in function 'on_tick'
PavementDriveAssist/control.lua:83: in function <PavementDriveAssist/control.lua:82>

Did you know the stop sign won't work going backwards?

It would be great if the stop sign (or all sign for that matter) had an imput value too, so you could turn them on and off. If that were the case, the railcorssing would be simple to set, turn the sign on when red=1 and connect it to a rail light. No need for combinators or deciders