Evaluation of Messages on Changeable Message Signs as a Speed Control Measure in Highway Work Zones

The objective of this study is to measure the effectiveness of three commonly used changeable message sign (CMS) messages in reducing vehicular speeds and variances in highway work zones. This paper presents the results of a field study conducted on Interstate-90 in western New York State to evaluate the use of three different types of messages displayed on a CMS, as a speed control measure. The study included speed measurements of nearly 180,000 vehicles. The three types of CMS messages tested were: (1) $\mathit{\text{RIGHT}}\mid \mathit{\text{LANE}}\mid \mathit{\text{CLOSED}}\sim \mathit{\text{KEEP}}\mid \mathit{\text{LEFT}}$ ; (2) $\mathit{\text{WORK}}\mathit{\text{ZONE}}\mid \mathit{\text{MAX}}\mathit{\text{SPEED}}\mid \mathit{45}\mathit{MPH}\sim \mathit{\text{BE}}\mid \mathit{\text{PREPARED}}\mid \mathit{\text{TO}}\mathit{\text{STOP}}$ ; and (3) $\mathit{\text{LEFT}}\mid \mathit{\text{LANE}}\mid \mathit{\text{CLOSED}}\sim \mathit{\text{KEEP}}\mid \mathit{\text{RIGHT}}$ . Of the three CMS messages tested, the CMS message stating “ $\mathit{\text{WORK}}\mathit{\text{ZONE}}\mid \mathit{\text{MAX}}\mathit{\text{SPEED}}\mid \mathit{45}\mathit{MPH}\sim \mathit{\text{BE}}\mid \mathit{\text{PREPARED}}\mid \mathit{\text{TO}}\mathit{\text{STOP}}$ ” proved the most effective, significantly reducing vehicle speeds by $3.3–6.7\mathrm{mi}∕\mathrm{h}$ $(5.3–10.8\mathrm{km}∕\mathrm{h})$ . The other two CMS messages were not as effective. The standard deviation of speed for the CMS message: $\mathit{\text{WORK}}\mathit{\text{ZONE}}\mid \mathit{\text{MAX}}\mathit{\text{SPEED}}\mid \mathit{45}\mathit{MPH}\sim \mathit{\text{BE}}\mid \mathit{\text{PREPARED}}\mid \mathit{\text{TO}}\mathit{\text{STOP}}$ increased by $1.1–1.7\mathrm{mi}∕\mathrm{h}$ $(1.8–2.7\mathrm{km}∕\mathrm{h})$ in the driving lane and $0.2–2.0\mathrm{mi}∕\mathrm{h}$ $(0.3–3.2\mathrm{km}∕\mathrm{h})$ in the passing lane. The speed variances for the other two CMS messages ranged from $-2.00\text{to}1.13\mathrm{mi}∕\mathrm{h}$ (from $-3.23\mathrm{km}∕\mathrm{h}\text{to}1.83\mathrm{km}∕\mathrm{h}$ ).