Index: src/economy.cpp
===================================================================
--- src/economy.cpp	(revision 9339)
+++ src/economy.cpp	(working copy)
@@ -1114,32 +1114,41 @@
 
 int32 GetTransportedGoodsIncome(uint num_pieces, uint dist, byte transit_days, CargoID cargo_type)
 {
-	CargoID cargo = cargo_type;
+	const int MIN_TIME_FACTOR = 31;
+	const int MAX_TIME_FACTOR = 255;
+
 	const CargoSpec *cs = GetCargo(cargo_type);
-	byte f;
+	const int days1 = cs->transit_days[0];
+	const int days2 = cs->transit_days[1];
+	const int days_over_days1 = transit_days - days1;
 
+	int time_factor;
+
 	/* zero the distance if it's the bank and very short transport. */
 	if (_opt.landscape == LT_NORMAL && cs->label == 'VALU' && dist < 10)
 		dist = 0;
 
-	f = 255;
-	if (transit_days > cs->transit_days[0]) {
-		transit_days -= cs->transit_days[0];
-		f -= transit_days;
+	/*
+	 * The time factor is calculated based on the time it took
+	 * (transit_days) compared two cargo-depending values. The
+	 * range is divided into three parts:
+	 *
+	 *  - constant for fast transits
+	 *  - linear decreasing with time with a slope of -1 for medium transports
+	 *  - linear decreasing with time with a slope of -2 for slow transports
+	 *
+	 */
+	if (days_over_days1 <= 0)
+		time_factor = MAX_TIME_FACTOR;
+	else if (days_over_days1 <= days2)
+		time_factor = MAX_TIME_FACTOR - days_over_days1;
+	else
+		time_factor = MAX_TIME_FACTOR - 2 * days_over_days1 + days2;
 
-		if (transit_days > cs->transit_days[1]) {
-			transit_days -= cs->transit_days[1];
+	if (time_factor < MIN_TIME_FACTOR)
+		time_factor = MIN_TIME_FACTOR;
 
-			if (f < transit_days) {
-				f = 0;
-			} else {
-				f -= transit_days;
-			}
-		}
-	}
-	if (f < 31) f = 31;
-
-	return BIGMULSS(dist * f * num_pieces, _cargo_payment_rates[cargo], 21);
+	return BIGMULSS(dist * time_factor * num_pieces, _cargo_payment_rates[cargo_type], 21);
 }
 
 static void DeliverGoodsToIndustry(TileIndex xy, CargoID cargo_type, int num_pieces)