Is driving in a hot vehicle safe?

Figures & data

Figure 1. Experimental set-up.

Figure 2. Time evolution of the air temperature in the vehicles, for all the 12 tests performed. Legend: test date (month_day).

Table 1. Synthesis of test results: t_out is the mean outdoor air temperature (measured), t₀ is the initial air temperature inside the vehicle (measured), t_∞ is the asymptotic air temperature, i.e. the limit temperature for time→∞, inside the vehicle (predicted), τ is the cooling timescale, σ is the r.m.s. of departures of the fit to the air temperatures inside the vehicle from experimental data.

Test date (month_day)	Vehicle*	tout (°C)	t0 (°C)	t∞ (°C)	τ (min)	σ (°C)
Jul_03	B	27.2	53.3	35.0	3.22	0.29
Jul_05	D	30.2	59.4	35.7	4.48	0.21
Jul_10	B	29.7	59.7	36.0	3.74	0.39
Jul_30	A	31.5	59.7	38.3	3.47	0.89
Jul_31	A	32.4	61.3	37.2	3.53	0.52
Aug_01	D	32.8	59.2	39.3	3.12	0.20
Aug_02	A	34.2	56.6	36.2	6.13	0.29
Aug_06	B	35.3	66.7	44.6	3.90	0.49
Aug_07	B	35.7	66.9	45.3	3.94	0.40
Aug_29	A	33.0	55.1	32.1	4.16	0.40
Sep_04	B	31.3	61.0	28.3	4.18	0.50
Sep_05	C	28.2	55.5	29.2	6.27	0.82

*A–Nissan Micra, dark grey, B–Toyota Auris, light grey, C–Fiat Cubo, light grey, D–Opel Astra, black.

Figure 3. Time evolution of the air temperature t_a and the globe temperature t_g in the vehicles, for four selected tests. Grey symbols: t_a; black symbols: t_g. Legend: test date (month_day).

Figure 4. Time evolution of the relative humidity in the vehicles, for all the 12 tests performed. Legend: test date (month_day).

Figure 5. Time evolution of the driver’s core (rectal) temperature during the first sixty minutes of driving, as predicted by the thermal model. Legend: test date (month_day).

Figure 6. Predicted relative performance as a function of the driver’s core temperature. Solid curve: demanding tasks; dashed curve: simple tasks; dots: literature experimental data for office tasks [25].

Table 2. Predicted relative performance in driving-related tasks during experimental tests: t_out is the mean outdoor air temperature (measured), t_core the core (rectal) temperature after 60 minutes of driving (predicted). Performance is set equal to 1 under ideal thermal conditions.

			Relative Performance
Test date (month_day)	tout (°C)	tcore (°C)	Demanding tasks	Simple tasks
Jul_03	27.2	37.07	0.81	0.94
Jul_05	30.2	37.08	0.74	0.91
Jul_10	29.7	37.07	0.81	0.94
Jul_30	31.5	37.09	0.68	0.89
Jul_31	32.4	37.12	0.55	0.83
Aug_01	32.8	37.20	0.16	0.57
Aug_02	34.2	37.08	0.75	0.91
Aug_06	35.3	37.21	0.13	0.53
Aug_07	35.7	37.23	0.10	0.50
Aug_29	33.0	37.00	1.00	1.00
Sep_04	31.3	37.04	0.94	0.98
Sep_05	28.2	37.00	1.00	1.00

Figure 7. Predicted relative performance as a function of the outdoor air temperature. Circles: demanding tasks; squares: simple tasks. Solid curve: best fit for demanding tasks; dashed curve: best fit for simple tasks.

Daanen HAM, van der Vliert E, Huang X. Driving performance in cold, warm, and thermoneutral environments. Appl Ergon 2003;34:597–602

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