104.28 Speed Display Trailer (Sdt)
2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS CATEGORY 100 PRELIMINARY SECTION 104.28 — SPEED DISPLAY TRAILER (SDT)
104.28.01 Description
Furnish, install and relocate a portable, self-contained, trailer mounted, dynamic speed display with static speed limit sign.
104.28.02 Materials
Speed Display Trailer QPL Each unit shall include the trailer, structural support system, sign panel assembly, lift mechanism, power supplies, sign mounted controller, non-invasive speed detection device, and ancillary equipment. All materials for the SDT shall be like new, corrosion resistant, and unaffected by water spray, salt, oil, gasoline, and all other contaminants in the quantities normally found along the edge of the traveled roadway. Construction, materials, and operation shall be in accordance with NFPA, ULI, and NEC. Sign messages shall be visible for a distance of 0.5 mile and legible for a distance of 900 ft from any point along the traveled approach roadway at all times.
104.28.02 01 Equipment. Trailer. In accordance with Maryland Motor Vehicle Law governing trailers. Structural Support. Refer to 104.19
Sign Panel. Sign panel dimensions shall not exceed 48 in. wide by 60 in. high. Display.
a.Each line of text shall be constructed using either a full or discrete matrix display. (b) The character height shall be at least 16 in. (c) If discrete matrix display is used, each character shall be displayed using a 5 x 7 array with at least two array modules per line.
104.28 Speed Display Trailer (Sdt)
2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
d.If a full matrix display is used, the sign shall have a pixel arrangement of at least 5 rows by 7 columns with 3 LEDs per pixel.
e.Attach one R2-1 (48 in. x 60 in.) Speed Limit sign to the trailer. The sign shall be easily removed and replaced. LED Illumination. LED illumination for each matrix element shall have the following characteristics:
a.LED shall conform to the ITE specification for amber color for warning applications.
b.Each LED shall produce at least 1 candela output on center at operating drive current. (c) LED shall provide full illumination within at least a 24 degree cone perpendicular to the sign face.
d.Operating temperature range of the LED shall be -30 F to 125 F. SDT Unit. Submit a catalog cut and character set for any SDT approval to the Office of Traffic and Safety, Chief of Traffic Operations. Lift Mechanism.
a.The lift mechanism shall be installed such that the sign panel can be raised and lowered manually.
b.A stainless steel safety bolt shall be provided to prevent the sign panel from lowering once in the raised position. A self-locking mechanism shall be incorporated into the safety bolt to prevent it from being inadvertently dislodged. Electrical Connections and Gauges.
a.All wiring from power sources to SDT equipment shall use locking cable connectors.
b.Volt and amp gauges shall be provided for both AC and DC. (c) Standard negative ground system shall be tied to the sign chassis. Power Supply. The SDT shall operate from a solar powered electrical system. This system shall consist of battery power system and solar array panels and be capable of displaying and storing vehicle speeds for 21 consecutive days without an auxiliary charge. Sign Controller. The controller shall:
a.Be capable of driving the matrix display panel operating over a -30 F to 125 F range and in a 20 percent to 95 percent noncondensing humidity range.
104.28 Speed Display Trailer (Sdt)
2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
b.Be designed for fail-safe prevention of improper information display in the case of a system malfunction.
c.Monitor and display the battery output voltage and solar array activities (charging and discharging). The controller shall blank the sign when the battery output voltage drops below the manufacturer’s recommended output level.
d.Be capable of monitoring and displaying the status of the photocell and adjusting the sign illumination to match the ambient light conditions. The controller shall have at least nine levels of dimming from 10 percent to 100 percent brightness.
e.Be contained in a sheet metal or high density polyethylene (HDPE), weatherproof cabinet located on the controller housing, and insulated to protect against excessive vibration and temperature. The cabinet shall have a lockable door latch and interior cabinet dome light.
f.Be capable of storing vehicle speed readings with a time and date stamp and have sufficient memory to store 100 000 readings.
g.Be capable of having remote access to modify sign messages, speed thresholds, and download vehicle speed readings. Speed Display Software.
a.The SDT shall be supplied with a non-invasive speed detection unit. The unit shall be able to be rotated on a separate vertical axis from the SDT to allow for better aiming and detection. The unit shall detect and display the speed of only approaching traffic.
b.The speed display software shall be able to display vehicle speeds that are traveling over a set threshold. The SDT shall also be capable of not displaying a vehicle speed over a separate set threshold. The speed display software shall have the capability of modifying speed thresholds.
104.28.03 Construction
Set up and operate the SDT on the project site 24 hours in advance of actual use to ensure that each unit is functioning properly and approved. Aim the SDT at approaching traffic that is at least 900 ft in advance of the SDT and in accordance with the 0.5 mile minimum visibility and 900 ft minimum legibility requirement. Ensure that the SDT is level and that the sign face is not obscured by highway alignment or glare from either sunlight or vehicle headlights.
104.28 Speed Display Trailer (Sdt)
2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
104.28.04 Measurement and Payment
The Speed Display Trailer will be measured and paid for at the Contract price per unit day. A unit day shall consist of any approved usage within a 24 hour calendar day period. Each Speed Display Trailer will be paid for only once per unit day, regardless of how many times it is relocated. When a unit is used for part of a day, it will be measured as a unit day. The payment will be full compensation for the setup and maintenance of computer programs, changing messages, and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
104.29 Truck Mounted Variable Message Sign (Tvms)
2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS CATEGORY 100 PRELIMINARY SECTION 104.29 — TRUCK MOUNTED VARIABLE MESSAGE SIGN (TVMS)
104.29.01 Description
Furnish, install and relocate a portable, self-contained, truck mounted, variable message sign.
104.29.02 Materials
Each unit shall contain the work vehicle structural support system, sign panel assembly, lift mechanism, power supplies, sign mounted controller, and ancillary equipment. All materials for TVMS shall be like new, corrosion resistant, and unaffected by water spray, salt, oil, gasoline, and all other contaminants in the quantities normally found along the edge of the traveled roadway. The TVMS construction, materials, and operation shall meet NFPA, UL, and NEC. Ensure that sign messages are visible and legible for a distance of 900 ft from any point along the traveled approach roadway at all times. The TVMS shall not block the driver’s rear view vision when either in the transport or the deployed position.
104.29.03 Construction
104.29.03 01 Equipment.
Truck. The work vehicle size and the method of attachment shall be as specified in the manufacturer's specifications. All vehicles shall be in accordance with Maryland Motor Vehicle Law. Structural Support. The structural support framework shall allow the system to be assembled into a unit and be mounted on the truck and shall provide the support mechanism between the sign panel assembly, the power supply, and the controller. The framework shall provide sufficient support to prevent damage to any TVMS components when the sign is in the down and locked position during normal highway travel. The sign panel shall be mounted as a permanent fixture of the truck and provide a minimum height of 7 ft from the bottom of the sign to the surface of the roadway when in its operating position. Affixing a trailer mounted unit to a truck is prohibited.
Source: Maryland Standard Specifications for Construction and Materials, 2025 Edition. Pages 217–220 of 1,113.