BALANCING AMBULANCE CREW WORKLOADS VIA A TIERED DISPATCH POLICY

Li, Xun; Saydam, Cem

doi:10.1590/0101-7438.2016.036.03.0399

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Articles • Pesqui. Oper. 36 (3) • Sep-Dec 2016 • https://doi.org/10.1590/0101-7438.2016.036.03.0399 copy

BALANCING AMBULANCE CREW WORKLOADS VIA A TIERED DISPATCH POLICY^* * Invited paper.

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Emergency Medical Services (EMS) system’s mission is to provide timely and effective treatment to anyone in need of urgent medical care throughout their jurisdiction. The default dispatch policy is to send the nearest ambulance to all medical emergencies and it is widely accepted by many EMS providers. However, sending nearest ambulance is not always optimal, often imposes heavy workloads on ambulance crews posted in high demand zones while reducing available coverage or requiring ambulance relocations to ensure high demand zones are covered adequately. In this paper we propose a tiered dispatch policy to balance the ambulance crew workloads while meeting fast response times for priority 1 calls. We use a tabu search algorithm to determine the initial ambulance locations and a simulation model to evaluate the impact of a tiered dispatch policy on ambulance crew workloads, coverage rates for priority 1-3 calls, and on survivability rate for out of hospital cardiac arrests. We present computational statistics and demonstrate the efficacy of the tiered dispatch policy using real-world data.

Keywords:
EMS; dispatching; call priorities; simulation

Interval	Monday		Tuesday		Wednesday		Thursday		Friday		Saturday		Sunday
	H	L	H	L	H	L	H	L	H	L	H	L	H	L
12 am - 2 am	11	15	14	21	13	19	14	19	15	20	19	24	17	27
2 am - 4 am	13	19	14	19	13	18	13	20	14	18	15	23	16	26
4 am - 6 am	12	15	13	14	12	15	13	15	14	16	13	18	13	19
6 am - 8 am	15	23	16	22	15	22	15	22	15	22	13	19	13	18
8 am - 10 am	17	29	18	30	17	31	17	30	18	29	16	25	15	24
10 am - 12 pm	19	34	19	33	17	33	18	33	19	33	18	29	17	28
12 pm - 2 pm	19	34	19	33	18	35	19	34	19	34	19	32	18	30
2 pm - 4 pm	19	36	19	33	19	33	18	34	19	36	18	32	18	31
4 pm - 6 pm	18	37	19	35	18	35	18	35	19	38	18	32	16	29
6 pm - 8 pm	17	35	19	33	16	31	16	32	17	32	18	33	16	30
8 pm - 10 pm	16	28	16	29	15	29	16	29	17	32	18	31	16	29
10 pm - 12 am	14	25	16	26	14	24	14	25	17	30	17	32	15	25

Monday High Workload Default Dispatch Policy
Intervals	OBJ-Fun	OHCA			P1			P2			P3			Workload
		Exp. Saved	Total	SF(%)	Covered	Total	%	Covered	Total	%	Covered	Total	%	AVG	STD	MIN	MAX	Range
12 am - 2 am	967.09	1.506	3	50.19	58	97	59.79	216	274	78.83	47	54	87.04	0.401	0.060	0.246	0.482	0.237
2 am - 4 am	926.98	1.499	3	49.95	51	77	66.23	225	249	90.36	45	50	90.00	0.453	0.104	0.196	0.606	0.410
4 am - 6 am	718.88	0.993	2	49.63	39	58	67.24	178	200	89.00	35	35	100.00	0.386	0.097	0.229	0.544	0.315
6 am - 8 am	1431.86	1.491	3	49.70	92	141	65.25	303	365	83.01	66	75	88.00	0.482	0.051	0.377	0.569	0.192
8 am - 10 am	1791.10	2.006	4	50.16	103	199	51.76	416	525	79.24	103	118	87.29	0.588	0.065	0.466	0.697	0.230
10 am - 12 pm	2314.77	3.048	6	50.81	145	244	59.43	496	621	79.87	114	139	82.01	0.606	0.069	0.455	0.746	0.291
12 pm - 2 pm	2131.61	2.038	6	33.96	128	238	53.78	477	608	78.45	121	136	88.97	0.605	0.074	0.459	0.718	0.259
2 pm - 4pm	2217.16	3.010	6	50.17	137	247	55.47	479	627	76.40	115	139	82.73	0.641	0.062	0.507	0.742	0.235
4 pm - 6 pm	2101.70	2.544	6	42.40	129	247	52.23	461	629	73.29	107	139	76.98	0.659	0.067	0.538	0.777	0.239
6 pm - 8 pm	1831.67	2.042	4	51.04	108	209	51.67	416	541	76.89	103	120	85.83	0.621	0.074	0.472	0.717	0.245
8 pm - 10 pm	1541.44	1.528	3	50.92	91	169	53.85	353	448	78.79	83	98	84.69	0.554	0.073	0.403	0.714	0.311
10 pm - 12 am	1360.39	1.524	3	50.80	84	138	60.87	299	364	82.14	66	75	88.00	0.525	0.081	0.325	0.623	0.298
	Sum	23.228	49			Avg=	58.13			80.52			86.80	0.543	Avg=	0.389	0.661	0.272

Monday High Workload Least Utilization Policy
Intervals	OBJ-Fun	OHCA			P1			P2			P3			Workload
		Exp. Saved	Total	SF(%)	covered	Total	%	covered	Total	%	Covered	Total	%	AVG	STD	MIN	MAX	Range
12 am - 2 am	863.09	1.506	3	50.19	58	97	59.79	165	274	60.22	45	54	83.33	0.421	0.007	0.41	0.433	0.023
2 am - 4 am	802.98	1.499	3	49.95	52	77	67.53	159	249	63.86	45	50	90.00	0.473	0.007	0.464	0.484	0.021
4 am - 6 am	662.88	0.993	2	49.63	39	58	67.24	150	200	75.00	35	35	100.00	0.400	0.041	0.268	0.439	0.172
6 am - 8 am	1256.86	1.491	3	49.70	88	141	62.41	231	365	63.29	67	75	89.33	0.499	0.009	0.484	0.514	0.030
8 am - 10 am	1559.10	2.006	4	50.16	99	199	49.75	318	525	60.57	99	118	83.90	0.612	0.024	0.517	0.630	0.114
10 am - 12 pm	1944.03	2.565	6	42.74	125	244	51.23	394	621	63.45	115	139	82.73	0.625	0.026	0.518	0.645	0.127
12 pm - 2 pm	1903.42	3.026	6	50.44	129	238	54.20	351	608	57.73	121	136	88.97	0.623	0.016	0.556	0.640	0.084
2 pm - 4pm	1906.16	3.010	6	50.17	124	247	50.20	371	627	59.17	124	139	89.21	0.654	0.026	0.546	0.670	0.124
4 pm - 6 pm	1828.70	2.544	6	42.40	117	247	47.37	371	629	58.98	110	139	79.14	0.673	0.040	0.508	0.693	0.185
6 pm - 8 pm	1591.67	2.042	4	51.04	104	209	49.76	312	541	57.67	103	120	85.83	0.639	0.009	0.625	0.662	0.036
8 pm - 10 pm	1390.44	1.528	3	50.92	89	169	52.66	286	448	63.84	82	98	83.67	0.569	0.049	0.434	0.594	0.160
10 pm - 12 am	1179.39	1.524	3	50.80	82	138	59.42	216	364	59.34	67	75	89.33	0.545	0.042	0.425	0.572	0.147
	Sum	23.732	49			Avg=	55.96			61.93			87.12	0.561	Avg=	0.480	0.581	0.102

Mean Difference	High Average Workload		Low Average Workload
	DEF - LU		DEF - LU
	Diff.	P-value	Diff.	P-value
OHCA	-0.0070	0.33*	0.0000	NA
P1 Coverage	0.0217	< 0.01	0.0491	< 0.01
P2 Coverage	0.1860	< 0.01	0.2670	< 0.01
P3 Coverage	-0.0033	0.34*	0.0034	0.12*
WL range	0.1699	< 0.01	0.3103	< 0.01

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[1] **Corresponding author.

Brasil

Brasil

BALANCING AMBULANCE CREW WORKLOADS VIA A TIERED DISPATCH POLICY* * Invited paper.

ABSTRACT

BALANCING AMBULANCE CREW WORKLOADS VIA A TIERED DISPATCH POLICY^* * Invited paper.