Fix lots of things around new LZB

9 files changed, 183 insertions, 99 deletions

diff --git a/advtrains/api_doc.txt b/advtrains/api_doc.txt
index 0256713..8ac4986 100644
--- a/advtrains/api_doc.txt
+++ b/advtrains/api_doc.txt
@@ -182,9 +182,11 @@ minetest.register_node(nodename, {
 		^- called when a train leaves the rail
 		
 		-- The following function is only in effect when interlocking is enabled:
-		on_train_approach = function(pos, train_id, train, index, lzbdata)
+		on_train_approach = function(pos, train_id, train, index, has_entered, lzbdata)
 		^- called when a train is approaching this position, called exactly once for every path recalculation (which can happen at any time)
 		^- This is called so that if the train would start braking now, it would come to halt about(wide approx) 5 nodes before the rail.
+		^- has_entered: when true, the train is already standing on this node with its front tip, and the enter callback has already been called.
+		   Possibly, some actions need not to be taken in this case. Only set if it's the very first node the train is standing on.
 		^- lzbdata should be ignored and nothing should be assigned to it
 	}
 })
diff --git a/advtrains/init.lua b/advtrains/init.lua
index 06ac66b..fead01e 100644
--- a/advtrains/init.lua
+++ b/advtrains/init.lua
@@ -27,8 +27,10 @@ attrans = minetest.get_translator ("advtrains")
 
 --advtrains
 
-DUMP_DEBUG_SAVE = false
-GENERATE_ATRICIFIAL_LAG = false
+local DUMP_DEBUG_SAVE = false
+local GENERATE_ATRICIFIAL_LAG = false
+local HOW_MANY_LAG = 1.0
+
 
 --Constant for maximum connection value/division of the circle
 AT_CMAX = 16
@@ -563,19 +565,12 @@ minetest.register_globalstep(function(dtime_mt)
 		
 		local dtime
 		if GENERATE_ATRICIFIAL_LAG then
-			dtime = 0.2
+			dtime = HOW_MANY_LAG
 			if os.clock()<t then
 				return
 			end
 			
-			t = os.clock()+0.2
-		else
-			--limit dtime: if trains move too far in one step, automation may cause stuck and wrongly braking trains
-			dtime=dtime_mt
-			if dtime>0.2 then
-				atprint("Limiting dtime to 0.2!")
-				dtime=0.2
-			end
+			t = os.clock()+HOW_MANY_LAG
 		end
 		
 		advtrains.mainloop_trainlogic(dtime)
diff --git a/advtrains/lzb.lua b/advtrains/lzb.lua
index 706f825..c4b3a27 100644
--- a/advtrains/lzb.lua
+++ b/advtrains/lzb.lua
@@ -18,13 +18,22 @@ train.lzb = {
 			-- Table of custom data filled in by approach callbacks
 			-- Whenever an approach callback inserts an LZB checkpoint with changed lzbdata,
 			-- all consecutive approach callbacks will see these passed as lzbdata table.
+			
+			udata = arbitrary user data, no official way to retrieve (do not use)
 		}
 	trav_lzbdata = currently active lzbdata table at traverser index
 }
-each step, for every item in "oncoming", we need to determine the location to start braking (+ some safety margin)
-and, if we passed this point for at least one of the items, initiate brake.
-When speed has dropped below, say 3, decrease the margin to zero, so that trains actually stop at the signal IP.
-The spd variable and travsht need to be updated on every aspect change. it's probably best to reset everything when any aspect changes
+The LZB subsystem keeps track of "checkpoints" the train will pass in the future, and has two main tasks:
+1. run approach callbacks, and run callbacks when passing LZB checkpoints
+2. keep track of the permitted speed at checkpoints, and make sure that the train brakes accordingly
+To perform 2, it populates the train.path_speed table which is handled along with the path subsystem.
+This table is used in trainlogic.lua/train_step_b() and applied to the velocity calculations.
+
+Note: in contrast to node enter callbacks, which are called when the train passes the .5 index mark, LZB callbacks are executed on passing the .0 index mark!
+If an LZB checkpoint has speed 0, the train will still enter the node (the enter callback will be called), but will stop at the 0.9 index mark (for details, see SLOW_APPROACH in trainlogic.lua)
+
+The start point for the LZB traverser (and thus the first node that will receive an approach callback) is floor(train.index) + 1. This means, once the LZB checkpoint callback has fired,
+this path node will not receive any further approach callbacks for the same approach situation
 ]]
 
 
@@ -61,6 +70,7 @@ local function resolve_latest_lzbdata(ckp, index)
 			return ckpi.lzbdata
 		end
 	end
+	return {}
 end
 
 local function look_ahead(id, train)
@@ -75,9 +85,11 @@ local function look_ahead(id, train)
 	local lzb = train.lzb
 	local trav = lzb.trav_index
 	-- retrieve latest lzbdata
-	local lzbdata = lzb.trav_lzbdata
-
-	if lzbdata.off_track then
+	if not lzb.trav_lzbdata then
+		lzb.trav_lzbdata = resolve_latest_lzbdata(lzb.checkpoints, trav)
+	end
+	
+	if lzb.trav_lzbdata.off_track then
 		--previous position was off track, do not scan any further
 	end
 	
@@ -85,8 +97,8 @@ local function look_ahead(id, train)
 		local pos = advtrains.path_get(train, trav)
 		-- check offtrack
 		if trav - 1 == train.path_trk_f then
-			lzbdata.off_track = true
-			advtrains.lzb_add_checkpoint(train, trav - 1, 0, nil, lzbdata)
+			lzb.trav_lzbdata.off_track = true
+			advtrains.lzb_add_checkpoint(train, trav - 1, 0, nil, lzb.trav_lzbdata)
 		else
 			-- run callbacks
 			-- Note: those callbacks are defined in trainlogic.lua for consistency with the other node callbacks
@@ -101,6 +113,27 @@ local function look_ahead(id, train)
 	
 end
 
+local function call_runover_callbacks(id, train)
+	if not train.lzb then return end
+	
+	local i = 1
+	local idx = atfloor(train.index)
+	local ckp = train.lzb.checkpoints
+	while ckp[i] do
+		if ckp[i].index <= idx then
+			-- call callback
+			local it = ckp[i]
+			if it.callback then
+				it.callback(it.pos, id, train, it.index, it.speed, train.lzb.lzbdata)
+			end
+			-- note: lzbdata is always defined as look_ahead was called before
+			table.remove(ckp, i)
+		else
+			i = i + 1
+		end
+	end
+end
+
 -- Flood-fills train.path_speed, based on this checkpoint 
 local function apply_checkpoint_to_path(train, checkpoint)
 	if not checkpoint.speed then
@@ -145,8 +178,7 @@ s = v0 * -------  +  - * | ------- |    =  -----------
 -- Removes all LZB checkpoints and restarts the traverser at the current train index
 function advtrains.lzb_invalidate(train)
 	train.lzb = {
-		trav_index = atround(train.index),
-		trav_lzbdata = {},
+		trav_index = atfloor(train.index) + 1,
 		checkpoints = {},
 	}
 end
@@ -175,7 +207,8 @@ end
 -- Add LZB control point
 -- lzbdata: If you modify lzbdata in an approach callback, you MUST add a checkpoint AND pass the (modified) lzbdata into it.
 -- If you DON'T modify lzbdata, you MUST pass nil as lzbdata. Always modify the lzbdata table in place, never overwrite it!
-function advtrains.lzb_add_checkpoint(train, index, speed, callback, lzbdata)
+-- udata: user-defined data, do not use externally
+function advtrains.lzb_add_checkpoint(train, index, speed, callback, lzbdata, udata)
 	local lzb = train.lzb
 	local pos = advtrains.path_get(train, index)
 	local lzbdata_c = nil
@@ -190,6 +223,7 @@ function advtrains.lzb_add_checkpoint(train, index, speed, callback, lzbdata)
 		speed = speed,
 		callback = callback,
 		lzbdata = lzbdata_c,
+		udata = udata,
 	}
 	table.insert(lzb.checkpoints, ckp)
 	
@@ -212,5 +246,5 @@ advtrains.te_register_on_update(function(id, train)
 		return
 	end
 	look_ahead(id, train)
-	--apply_control(id, train)
+	call_runover_callbacks(id, train)
 end, true)
diff --git a/advtrains/trainlogic.lua b/advtrains/trainlogic.lua
index 9e9f021..c0c2e93 100644
--- a/advtrains/trainlogic.lua
+++ b/advtrains/trainlogic.lua
@@ -56,6 +56,13 @@ local VLEVER_ROLL = 2
 local VLEVER_HOLD = 3
 local VLEVER_ACCEL = 4
 
+-- How far in front of a whole index with LZB 0 restriction the train should come to a halt
+-- value must be between 0 and 0.5, exclusively
+local LZB_ZERO_APPROACH_DIST = 0.1
+-- Speed the train temporarily approaches the stop point with
+local LZB_ZERO_APPROACH_SPEED = 0.2
+
+
 
 tp_player_tmr = 0
 
@@ -256,7 +263,6 @@ function advtrains.train_ensure_init(id, train)
 	--assertdef(train, "tarvelocity", 0)
 	assertdef(train, "acceleration", 0)
 	assertdef(train, "id", id)
-	assertdef(train, "ctrl", {})
 	
 	
 	if not train.drives_on or not train.max_speed then
@@ -350,11 +356,9 @@ function advtrains.train_step_b(id, train, dtime)
 		v_target_apply(v_targets, VLEVER_ROLL, 0)
 	end
 	
-	--- 3a. this can be useful for debugs/warnings and is used for check_trainpartload ---
-	local t_info, train_pos=sid(id), advtrains.path_get(train, atfloor(train.index))
-	if train_pos then
-		t_info=t_info.." @"..minetest.pos_to_string(train_pos)
-		--atprint("train_pos:",train_pos)
+	-- interlocking speed restriction
+	if train.speed_restriction then
+		v_target_apply(v_targets, VLEVER_BRAKE, train.speed_restriction)
 	end
 	
 	--apply off-track handling:
@@ -374,7 +378,7 @@ function advtrains.train_step_b(id, train, dtime)
 	--interpret ATC command and apply auto-lever control when not actively controlled
 	local v0 = train.velocity
 	
-	if train.ctrl.user then
+	if train.ctrl_user then
 		advtrains.atc.train_reset_command(train)
 	else
 		local braketar = train.atc_brake_target
@@ -405,7 +409,6 @@ function advtrains.train_step_b(id, train, dtime)
 			train.atc_delay = nil
 		end
 		
-		train.ctrl.atc = nil
 		if train.tarvelocity and train.tarvelocity>v0 then
 			v_target_apply(v_targets, VLEVER_ACCEL, train.tarvelocity)
 		end
@@ -417,28 +420,47 @@ function advtrains.train_step_b(id, train, dtime)
 					v_target_apply(v_targets, VLEVER_EMERG, braketar)
 				end
 			else
-				v_target_apply(v_targets, VLEVER_ROLL, braketar)
+				v_target_apply(v_targets, VLEVER_ROLL, train.tarvelocity)
 			end
 		end
 	end
 	
+	local userc = train.ctrl_user
+	if userc then
+		v_target_apply(v_targets, userc, userc==VLEVER_ACCEL and train.max_speed or 0)
+	end
+	
 	--- 2b. look at v_target, determine the effective v_target and desired acceleration ---
 	local tv_target, tv_lever
-	for _,lever in ipairs({VLEVER_EMERG, VLEVER_BRAKE, VLEVER_ROLL, VLEVER_ACCEL}) do
+	
+	if v_targets[VLEVER_ACCEL] then
+		if v_targets[VLEVER_ACCEL] > v0 then
+			tv_target = v_targets[VLEVER_ACCEL]
+			tv_lever = VLEVER_ACCEL
+		end
+	end
+	for _,lever in ipairs({VLEVER_ROLL, VLEVER_BRAKE, VLEVER_EMERG}) do
 		if v_targets[lever] then
-			tv_target = v_targets[lever]
-			tv_lever = lever
-			break
+			if v_targets[lever] <= v0 then
+				if not tv_target then
+					tv_target = v_targets[lever]
+				else
+					tv_target = math.min(v_targets[lever], tv_target)
+				end
+			end
+			if v_targets[lever] < v0 then
+				tv_lever = lever
+			end
 		end
 	end
+	
+	--train.debug = dump({tv_target,tv_lever})
+	
 	--- 2c. If no tv_lever set, honor the user control ---
 	local a_lever = tv_lever
 	if not tv_lever then
-		a_lever = train.ctrl.user
-		if not a_lever then
-			-- default to holding current speed
-			a_lever = VLEVER_HOLD
-		end
+		-- default to holding current speed
+		a_lever = VLEVER_HOLD
 	end
 	
 	train.lever = a_lever
@@ -447,11 +469,15 @@ function advtrains.train_step_b(id, train, dtime)
 	-- Iterates over the path nodes we WOULD pass if we were continuing with the speed assumed by actual_lever
 	-- and determines the MINIMUM of path_speed in this range.
 	-- Then, determines acceleration so that we can reach this 'overridden' target speed in this step (but short-circuited)
+	local lzb_zeroappr_target_index
+	local new_index_v_base -- which v was assumed when curr_tv was calculated
+	local new_index_curr_tv -- pre-calculated new train index in lzb check
+	
 	if not a_lever or a_lever > VLEVER_BRAKE then
 		-- only needs to run if we're not yet braking anyway
-		local tv_vdiff = advtrains.get_acceleration(train, tv_lever) * dtime
-		local dst_curr_v = (v0 + tv_vdiff) * dtime
-		local nindex_curr_v = advtrains.path_get_index_by_offset(train, train.index, dst_curr_v)
+		new_index_v_base = v0 + (advtrains.get_acceleration(train, tv_lever) * dtime)
+		local dst_curr_v = new_index_v_base * dtime
+		new_index_curr_tv = advtrains.path_get_index_by_offset(train, train.index, dst_curr_v)
 		local i = atfloor(train.index)
 		local lzb_target
 		local psp
@@ -460,17 +486,44 @@ function advtrains.train_step_b(id, train, dtime)
 			if psp then
 				lzb_target = lzb_target and math.min(lzb_target, psp) or psp
 			end
-			if i > nindex_curr_v then
+			if i > new_index_curr_tv then
 				break
 			end
 			i = i + 1
 		end
 		
-		local dv
+		--train.debug = "newindex calc "..new_index_curr_tv.." basev="..new_index_v_base.." lzbtarget="..(lzb_target or "nil")
+		
 		if lzb_target and lzb_target <= v0 then
 			-- apply to tv_target after the actual calculation happened
 			a_lever = VLEVER_BRAKE
-			tv_target = tv_target and math.min(tv_target, lzb_target) or lzb_target
+			if tv_target and tv_target > lzb_target then
+				if lzb_target < LZB_ZERO_APPROACH_SPEED then
+					--atdebug("hit zeroappr lzb=",lzb_target, "tv=", tv_target)
+					--go forward with LZB_ZERO_APPROACH_SPEED if tv_target didn't tell us otherwise
+					tv_target = LZB_ZERO_APPROACH_SPEED
+					-- find the zero index we're approaching
+					local lzb_zeroappr_target_index = math.ceil(train.index)
+					while train.path_speed[lzb_zeroappr_target_index] and train.path_speed[lzb_zeroappr_target_index] > 0 do
+						lzb_zeroappr_target_index = lzb_zeroappr_target_index + 1
+						--atdebug("zeroappr advancing ",lzb_zeroappr_target_index)
+					end
+					-- it should now point to an index with path_speed==0. In case of weird things, points to some far away index, so doesn't matter
+					lzb_zeroappr_target_index = lzb_zeroappr_target_index - LZB_ZERO_APPROACH_DIST
+					--atdebug("zeroappr target idx ",lzb_zeroappr_target_index)
+					-- don't do anything when we are already at this index, and stop
+					if train.index >= lzb_zeroappr_target_index then
+						tv_target = 0
+						a_lever = VLEVER_BRAKE
+						lzb_zeroappr_target_index = nil
+						--atdebug("zeroappr cancelling train has passed idx=",train.index, "za_idx=",lzb_zeroappr_target_index)
+					end
+				else
+					tv_target = lzb_target
+				end
+			end
+			
+			
 		end
 	end
 	
@@ -480,11 +533,13 @@ function advtrains.train_step_b(id, train, dtime)
 	local v1
 	local tv_effective = false
 	if tv_target and (math.abs(dv) > math.abs(tv_target - v0)) then
+		--atdebug("hit tv_target ",tv_target,"with v=",v0, "dv=",dv)
 		v1 = tv_target
 		tv_effective = true
 	else
 		v1 = v0 +dv
 	end
+	--train.debug = "tv_target="..(tv_target or "nil").." v0="..v0.." v1="..v1
 	
 	if v1 > train.max_speed then
 		v1 = train.max_speed
@@ -493,22 +548,23 @@ function advtrains.train_step_b(id, train, dtime)
 		v1 = 0
 	end
 	
-	train.acceleration = v1 - v0
+	train.acceleration = (v1 - v0) / dtime
 	train.velocity = v1
 	
 	--- 4. move train ---
+	-- if we have calculated the new end index before, don't do that again
+	if not new_index_v_base or new_index_v_base ~= v1 then
+		local tv_vdiff = advtrains.get_acceleration(train, tv_lever) * dtime
+		local dst_curr_v = v1 * dtime
+		new_index_curr_tv = advtrains.path_get_index_by_offset(train, train.index, dst_curr_v)
+	end
 	
-	local idx_floor = math.floor(train.index)
-	local pdist = (train.path_dist[idx_floor+1] - train.path_dist[idx_floor])
-	local distance = (train.velocity*dtime) / pdist
-	
-	--debugging code
-	--local debutg = advtrains.print_concat_table({"v0=",v0,"v1=",v1,"a_lever",a_lever,"tv_target",tv_target,"tv_eff",tv_effective})
-	--train.debug = debutg
-	
-	if advtrains.DFLAG and v1>0 then error("DFLAG") end
-	
-	train.index=train.index+distance
+	-- if the zeroappr mechanism has hit, go no further than zeroappr index
+	if lzb_zeroappr_target_index and new_index_curr_tv > lzb_zeroappr_target_index then
+		--atdebug("zeroappr hitcond newidx_tv=",new_index_curr_tv, "za_idx=",lzb_zeroappr_target_index)
+		new_index_curr_tv = lzb_zeroappr_target_index
+	end
+	train.index = new_index_curr_tv
 	
 	recalc_end_index(train)
 
@@ -636,8 +692,9 @@ local callbacks_enter_node, run_callbacks_enter_node = mknodecallback("enter")
 local callbacks_leave_node, run_callbacks_leave_node = mknodecallback("leave")
 
 -- Node callback for approaching
--- Might be called multiple times, whenever path is recalculated
--- signature is function(pos, id, train, index, lzbdata)
+-- Might be called multiple times, whenever path is recalculated. Also called for the first node the train is standing on, then has_entered is true.
+-- signature is function(pos, id, train, index, has_entered, lzbdata)
+-- has_entered: true if the "enter" callback has already been executed for this train in this location
 -- lzbdata: arbitrary data (shared between all callbacks), deleted when LZB is restarted.
 -- These callbacks are called in order of distance as train progresses along tracks, so lzbdata can be used to
 -- keep track of a train's state once it passes this point
@@ -693,14 +750,16 @@ end
 
 function advtrains.tnc_call_approach_callback(pos, train_id, train, index, lzbdata)
 	--atdebug("tnc approach",pos,train_id, lzbdata)
+	local has_entered = atround(train.index) == index
+	
 	local node = advtrains.ndb.get_node(pos) --this spares the check if node is nil, it has a name in any case
 	local mregnode=minetest.registered_nodes[node.name]
 	if mregnode and mregnode.advtrains and mregnode.advtrains.on_train_approach then
-		mregnode.advtrains.on_train_approach(pos, train_id, train, index, lzbdata)
+		mregnode.advtrains.on_train_approach(pos, train_id, train, index, has_entered, lzbdata)
 	end
 	
 	-- call other registered callbacks
-	run_callbacks_approach_node(pos, train_id, train, index, lzbdata)
+	run_callbacks_approach_node(pos, train_id, train, index, has_entered, lzbdata)
 end
 
 
diff --git a/advtrains/wagons.lua b/advtrains/wagons.lua
index 66d083e..c5e1e17 100644
--- a/advtrains/wagons.lua
+++ b/advtrains/wagons.lua
@@ -986,10 +986,10 @@ function wagon:show_bordcom(pname)
 	
 	-- Interlocking functionality: If the interlocking module is loaded, you can set the signal aspect
 	-- from inside the train
-	if advtrains.interlocking and train.lzb and #train.lzb.oncoming > 0 then
+	if advtrains.interlocking and train.lzb and #train.lzb.checkpoints > 0 then
 		local i=1
-		while train.lzb.oncoming[i] do
-			local oci = train.lzb.oncoming[i] --TODO repair this
+		while train.lzb.checkpoints[i] do
+			local oci = train.lzb.checkpoints[i]
 			if oci.udata and oci.udata.signal_pos then
 				if advtrains.interlocking.db.get_sigd_for_signal(oci.udata.signal_pos) then
 					form = form .. "button[4.5,8;5,1;ilrs;Remote Routesetting]"
diff --git a/advtrains_interlocking/approach.lua b/advtrains_interlocking/approach.lua
index 6157a17..0894043 100644
--- a/advtrains_interlocking/approach.lua
+++ b/advtrains_interlocking/approach.lua
@@ -19,32 +19,34 @@ local function get_over_function(speed, shunt)
 		if speed == 0 and minetest.settings:get_bool("at_il_force_lzb_halt") then
 			atwarn(id,"overrun LZB 0 restriction (red signal) ",pos)
 			-- Set train 1 index backward. Hope this does not lead to bugs...
-			train.index = index - 0.5
-			train.velocity = 0
-			train.ctrl.lzb = 0
-			minetest.after(0, advtrains.invalidate_path, id)
+			--train.index = index - 0.5
+			train.speed_restriction = 0
 		else
 			train.speed_restriction = speed
 			train.is_shunt = shunt
 		end
+		--atdebug("train drove over IP: speed=",speed,"shunt=",shunt)
 	end
 end
 
-advtrains.tnc_register_on_approach(function(pos, id, train, index, lzbdata)
+advtrains.tnc_register_on_approach(function(pos, id, train, index, has_entered, lzbdata)
 
 	--atdebug(id,"IL ApprC",pos,index,lzbdata)
 	--train.debug = advtrains.print_concat_table({train.is_shunt,"|",index,"|",lzbdata})
 
 	local pts = advtrains.roundfloorpts(pos)
 	local cn  = train.path_cn[index]
-	local travsht = lzbdata.travsht
+	local travsht = lzbdata.il_shunt
+	
+	local travspd = lzbdata.il_speed
 	
 	if travsht==nil then
-		travsht = train.is_shunt
+		-- lzbdata has reset
+		travspd = train.speed_restriction
+		travsht = train.is_shunt or false
 	end
 	
-	local travspd = lzbdata.travspd
-	local travwspd = lzbdata.travwspd
+	
 	
 	-- check for signal
 	local asp, spos = il.db.get_ip_signal_asp(pts, cn)
@@ -66,7 +68,7 @@ advtrains.tnc_register_on_approach(function(pos, id, train, index, lzbdata)
 	--atdebug("trav: ",pos, cn, asp, spos, "travsht=", lzb.travsht)
 	local lspd
 	if asp then
-		--atdebug(id,"IL Signal",spos,asp)
+		--atdebug(id,"IL Signal",spos, asp, lzbdata, "trainstate", train.speed_restriction, train.is_shunt)
 		local nspd = 0
 		--interpreting aspect and determining speed to proceed
 		if travsht then
@@ -95,26 +97,15 @@ advtrains.tnc_register_on_approach(function(pos, id, train, index, lzbdata)
 			end
 		end
 		
-		local nwspd = asp.info.w_speed
-		if nwspd then
-			if nwspd == -1 then
-				travwspd = nil
-			else
-				travwspd = nwspd
-			end
-		end
-		--atdebug("ns,wns,ts,wts", nspd, nwspd, travspd, travwspd)
+		--atdebug("ns,ts", nspd, travspd)
 		lspd = travspd
-		if travwspd and (not lspd or lspd>travwspd) then
-			lspd = travwspd
-		end
 		
 		local udata = {signal_pos = spos}
 		local callback = get_over_function(lspd, travsht)
-		lzbdata.travsht = travsht
-		lzbdata.travspd = travspd
-		lzbdata.travwspd = travwspd
-		advtrains.lzb_add_checkpoint(train, index, lspd, callback, lzbdata)
+		lzbdata.il_shunt = travsht
+		lzbdata.il_speed = travspd
+		--atdebug("new lzbdata",lzbdata)
+		advtrains.lzb_add_checkpoint(train, index, lspd, callback, lzbdata, udata)
 	end
 end)
 
diff --git a/advtrains_line_automation/stoprail.lua b/advtrains_line_automation/stoprail.lua
index 5af4399..4fdab51 100644
--- a/advtrains_line_automation/stoprail.lua
+++ b/advtrains_line_automation/stoprail.lua
@@ -169,7 +169,8 @@ local adefunc = function(def, preset, suffix, rotation)
 				show_stoprailform(pos, player)
 			end,
 			advtrains = {
-				on_train_approach = function(pos,train_id, train, index)
+				on_train_approach = function(pos,train_id, train, index, has_entered)
+					if has_entered then return end -- do not stop again!
 					if train.path_cn[index] == 1 then
 						local pe = advtrains.encode_pos(pos)
 						local stdata = advtrains.lines.stops[pe]
@@ -180,7 +181,7 @@ local adefunc = function(def, preset, suffix, rotation)
 								stdata.ars = {default=true}
 							end
 							if stdata.ars and (stdata.ars.default or advtrains.interlocking.ars_check_rule_match(stdata.ars, train) ) then
-								advtrains.lzb_add_checkpoint(train, index, 2, nil)
+								advtrains.lzb_add_checkpoint(train, index, 0, nil)
 								local stn = advtrains.lines.stations[stdata.stn]
 								local stnname = stn and stn.name or "Unknown Station"
 								train.text_inside = "Next Stop:\n"..stnname
diff --git a/advtrains_luaautomation/README.txt b/advtrains_luaautomation/README.txt
index 3e9a257..7c064cc 100644
--- a/advtrains_luaautomation/README.txt
+++ b/advtrains_luaautomation/README.txt
@@ -247,8 +247,10 @@ set_shunt(), unset_shunt()
 
 -- This additional function is available when advtrains_interlocking is enabled: --
 
-atc_set_disable_ars(true)
+atc_set_disable_ars(boolean)
 	Disables (true) or enables (false) the use of ARS for this train. The train will not trigger ARS (automatic route setting) on signals then.
+	Note: If you want to disable ARS from an approach callback, the call to atc_set_disable_ars(true) must happen during the approach callback,
+	and may not be deferred to an interrupt(). Else the train might trigger an ARS before the interrupt fires.
 
 # Approach callbacks
 The LuaATC interface provides a way to hook into the approach callback system, which is for example used in the TSR rails (provided by advtrains_interlocking) or the station tracks (provided by advtrains_lines). However, for compatibility reasons, this behavior needs to be explicitly enabled.
diff --git a/advtrains_luaautomation/atc_rail.lua b/advtrains_luaautomation/atc_rail.lua
index 0f5a7dc..6ce323d 100644
--- a/advtrains_luaautomation/atc_rail.lua
+++ b/advtrains_luaautomation/atc_rail.lua
@@ -199,7 +199,7 @@ advtrains.register_tracks("default", {
 					--do async. Event is fired in train steps
 					atlatc.interrupt.add(0, pos, {type="train", train=true, id=train_id})
 				end,
-				on_train_approach = function(pos, train_id, train, index, lzbdata)
+				on_train_approach = function(pos, train_id, train, index, has_entered, lzbdata)
 					-- Insert an event only if the rail indicated that it supports approach callbacks
 					local ph=minetest.pos_to_string(pos)
 					local railtbl = atlatc.active.nodes[ph]
@@ -208,7 +208,7 @@ advtrains.register_tracks("default", {
 					if railtbl and railtbl.data and railtbl.data.__approach_callback_mode then
 						local acm = railtbl.data.__approach_callback_mode
 						if acm==2 or (acm==1 and train.path_cn[index] == 1) then
-							local evtdata = {type="approach", approach=true, id=train_id}
+							local evtdata = {type="approach", approach=true, id=train_id, has_entered = has_entered}
 							-- This event is *required* to run synchronously, because it might set the ars_disable flag on the train and add LZB checkpoints,
 							-- although this is generally discouraged because this happens right in a train step
 							-- At this moment, I am not aware whether this may cause side effects, and I must encourage users not to do expensive calculations here.