Table 1.
Results of linear models with AR(1) covariance structures examining changes in trends post mid-2009 for Colorado and 34 NMMS and estimated generalized least squares models comparing Colorado and the 34 NMMS on the proportion of drivers in a fatal motor vehicle crash who were marijuana-positive and/or alcohol-impaired (not shown – intercept for Colorado models and 34 NMMS models; and NMMS intercept, NMMS trend before mid-2009, NMMS change in trend after mind-2009, and difference between 34 NMMS intercept and Colorado intercept for Colorado vs. 34 NMMS models)
| Proportion of Drivers in a Fatal Motor Vehicle Crash who were Marijuana-Positive | Proportion of Drivers in a Fatal Motor Vehicle Crash who were Alcohol-Impaired | |||||
|---|---|---|---|---|---|---|
| beta (standard error) | t | p | beta (standard error) | t | p | |
| Colorado | ||||||
| Trend before mid-2009 | −0.19 (0.08) | −2.40 | 0.0227 | 0.09 (0.12) | 0.74 | 0.4654 |
| Change in trend after mid-2009 | 2.16 (0.45) | 4.76 | 0.0001 | 0.06 (0.97) | 0.07 | 0.9476 |
| Proportion of male drivers | −0.11 (0.09) | −1.18 | 0.2484 | −0.15 (0.22) | −0.68 | 0.5002 |
| Proportion of drivers 21–24 years old | −0.12 (0.10) | −1.22 | 0.2328 | 0.06 (0.23) | 0.27 | 0.7889 |
| Proportion tested for drugs or alcohol | 0.11 (0.04) | 2.99 | 0.0056 | 0.39 (0.10) | 4.03 | 0.0004 |
| 34 NMMS | ||||||
| Trend before mid-2009 | 0.02 (0.05) | 0.35 | 0.7304 | −0.06 (0.05) | −1.12 | 0.2705 |
| Change in trend after mid-2009 | 0.11 (0.18) | 0.61 | 0.5447 | −0.01 (0.29) | −0.05 | 0.9619 |
| Proportion of male drivers | −0.10 (0.10) | −1.05 | 0.3042 | 0.39 (0.21) | 1.88 | 0.0693 |
| Proportion of drivers 21–24 years old | −0.02 (0.14) | −0.15 | 0.8810 | 0.53 (0.28) | 1.90 | 0.0667 |
| Proportion tested for drugs or alcohol | 0.13 (0.03) | 4.59 | 0.0001 | 0.23 (0.09) | 2.65 | 0.0128 |
| Colorado vs. 34 NMMS | ||||||
| Difference in trend before mid-2009 | −0.22 (0.06) | −3.65 | 0.0005 | 0.17 (0.20) | 0.85 | 0.3972 |
| Difference in change in trend after mid-2009 | 2.06 (0.48) | 4.30 | 0.0001 | 0.49 (1.64) | 0.30 | 0.7658 |
| Proportion of male drivers | −0.10 (0.06) | −1.69 | 0.0956 | 0.33 (0.14) | 2.35 | 0.0217 |
| Proportion of drivers 21–24 years old | −0.09 (0.08) | −1.17 | 0.2466 | 0.45 (0.20) | 2.30 | 0.0245 |
| Proportion tested for drugs or alcohol | 0.13 (0.02) | 5.83 | 0.0001 | 0.22 (0.06) | 3.60 | 0.0006 |