1.15.1. Certain signs in S13‑2 are intended to be displayed only during transient conditions. These include diagrams 551.1 (Migratory toad crossing, S13‑2‑1), 554A (Flood, S13‑2‑2), 554D (No smoking, S13‑2‑3), 554.2 (Ice, S13‑2‑4), 556 (Uneven road, S13‑2‑5), 557 (Slippery road, S13‑2‑6) and some applications of 562 with associated plate (Other danger, S13‑2‑7). They should be removed when the danger has passed. Diagram 7014 warns of a permanent change in road layout or new traffic signals etc. This sign must display a remove by date on the reverse, limited to a maximum period of three months after completion of the works (S13‑7‑8 and Direction 12). Such signs should be used sparingly and not as a matter of course. Diagram 7014.1 (S13‑6‑39) warns of a reduction in headroom at a bridge. Where this reduction is temporary, the sign may be retained only for the duration of the reduction. When a permanent reduction occurs, resulting in headroom of less than 16’‑6” (5.03 m), the sign may be retained for a period of six months and must display a remove by date on the reverse (see 7.3.4). Authorities that fail to comply with their statutory responsibilities to remove redundant signs not only devalue the signs but contribute to sign clutter.