T-M

Transportation Markings: Typology

 

There are thousands of Transportation-Markings in use. These range from tree branches stuck in mud banks of shallow rivers to orbiting satellites emitting GPS information on location. To try and sum up T-M forms in a few pictorial images can be a nearly impossible task. However, an informal typology of T-M types can provide a simple way of introducing T-M forms in a few images. T-M forms can be divided into these basic types: Visual (All-lighted, Partially-lighted, Unlighted), Sound, and Electronic aids. A more curious and less well known aid completes the typology. This aid, termed tactile, includes staffs, tickets, tokens and tablets on single-line rail lines.

All-lighted signals (e.g. Traffic and rail signals) display lighted messages day and night. Par-tially-lighted aids are those lighted only at night (e.g. lighthouses, and traditional obstruction beacons). Some partially-lighted aids have no day dimension (daymark in marine terms). Some aids with a day aspect may have a designed daymark attached to the aid while other days are simply the structure holding up the light apparatus. The accompanying image for all-lighted is a railway color-light signal. A traditional lighthouse represents partially-lighted forms and can suggest other traditional safety aids as well.

Unlighted visual aids comprise several sub-types: Signs with words and/or numbers and positioned vertically (e.g. traffic signs). A second type of sign employs the term more loosely. This type lacks alphanumeric symbols but may display stripes or bands (e.g. marker boards on railways that indicate distance to a lighted signal by the number of stripes). Another unlighted form consists of unlighted signals. These employ moving parts and can give multiple messages. (e.g. railway targets). A further type of unlighted aid is that of structural objects lacking lights,
moving parts and even alphanumeric messages (e.g. daybeacons and barricades). The final aid, surface markings, (horizontal) includes lines and other geometric shapes and possible alphanumeric symbols. Some essentially unlighted aids may employ indirect lighting or a light apparatus. The nature of these aids does not require the lighting dimension. Images are included for each of these forms.

Many notable traditional sound signals were in the form of fixed marine fog signals. However, many of these have been retired. More in evidence are buoy sound signals including bell, gong, and whistle buoys. Railway crossing bells and a limited number of pedestrial signals audible signals (including tweeters and bird calls). A bell buoy image represents sound signals and also represents the vast panorama of floating aids.

Electronic aids date back to the early 20th c. and have manifested a variety of forms from radio ranges and radio beacons to loran, omega and satellite navigation aids. A relatively new aid, GPS, has quickly eclipsed not only many lighted but also a variety of radio aids. An image of GPS represents electronic safety aids.

“Tactile” safety aids include a variety of objects that require physical possession by a train crew before a railway block can be entered. This form of aid has declined though some forms, including key token system, are still find use. The image is that of a token key.