Important sign types for highway expressways

(1) Charted Advance Signs

Charted advance signs are characterized by displaying clear, simple planar graphics on the sign face that visually reflect the roadway access ahead, including the direction of the exit, and the relationship to the mainline. Charted Advance Signs are coordinated in front of exits. The design and layout of chart-type advance warning signs are mainly characterized by the following features:

* Each arrow should not point to more than one destination, and more than two destinations should not be displayed on one sign;

* The length of the exit direction arrow is required to be shorter than that of the mainline forward arrow, and it should not be separated from the mainline arrows, to maintain the integrity of the pattern. However, if the bifurcation point separates evenly from the mainline and is not a clear exit bifurcation, the lengths of the arrows in both directions should be equal.

*Lane dividers are delineated within the main axis of the arrows and are compatible with the lane arrangement at the site.

*Shield route number, route direction. Destination and other information requirements can be clear, obvious judgment and the relationship between the arrow pointing to the general arrow pointing directly to the shield route number, indicating that the road ahead can be reached. Route direction information is set side by side in the shield-shaped route number next to the destination information is set in the lower part of the route number to play a mutually confirming, complementary role.

*Graphic warning signs are usually used for forecasting purposes and are therefore not usually placed at exit indications.

(2) Interchange Exit Numbering 

In the U.S., not only are the routes of the road network numbered, but also the interchange exits of each highway and expressway are systematically numbered to enhance the driver's sense of orientation and to make it easier to remember. The exit number is displayed on each exit warning sign, exit indication sign and triangle end indication sign of the interchange, and the exit number sign is separately blocked and attached to the upper edge of the warning sign and exit indication sign. The exit numbering sign is attached to the left side of the upper edge of the sign if the interchange exit is a left-hand exit, or to the right side of the upper edge of the sign if the exit is a right-hand exit. The information conveyed by the exit number sign includes "EXIT" and the coded number of the exit, but if the interchange exit is a left-hand exit, "LEFT" needs to be added above "EXIT" because drivers are accustomed to traveling on the right side of the road, and an advance warning is needed if the interchange exit is a left-hand exit in order for drivers to change lanes safely.

(3) Exit Advance Signs

Exit Advance Signs are installed on road sections close to the exit of interchanges to announce the major destinations that can be reached by the exit ahead, as well as the distance between the signage point and the exit. This kind of exit warning sign is usually used in the right side of the exit, if the exit of the interchange for the left side of the exit, the use of chart-type warning signs is more appropriate.

The content of the sign face of the exit warning sign is required to be consistent with the exit instruction sign, except that the exit instruction sign lacks distance information (EXIT MILES), the exit warning sign and the exit instruction sign should not display more than two destinations or street names, and to avoid simultaneous appearances of the name of the city and the street name on the same signage, if there is a need to display the name of two or three destinations in the same support frame, then it should be provide multiple sign faces and should not have more than 1 destination name per sign face. In addition, if the interchange has 2 or more exits in the same direction, the EXIT in the bottom row shall be in plural form (EXITS MILES); if there is an exit number sign attached to the upper edge of the sign, the EXITs in the bottom row may be omitted.

Regarding the layout of the exit warning signs, for large and medium-sized interchanges, the warning signs are set at 2km and 1km before the exit, and the third warning sign can be set at 4km if conditions permit. For small interchanges, only one advance warning sign can be set up within 1km to 2km from the exit.

(4) Next Exit Advance Sign

In the highway and expressway in the United States, if the distance between the current exit and the next exit is more than 8km, a Next Exit Advance Sign (NEXI EXIT) will be set up to inform the driver in advance of the exact distance to the next exit, so as to enable drivers to have a clear idea of what to expect. The next exit warning sign is generally attached to the lower edge of the nearest exit warning sign from the current exit, which conveys the message "NEXI EXIT -- km ( MILES )", the message content of the sign can be arranged in a row or two rows, but the effect of one row will be better, unless the message content is too long, then choose to arrange in two rows.

(5) Exit instruction sign

The information conveyed by the exit instruction sign is basically the same as that of the exit preview sign, which mainly includes the exit number, route number and direction, and destination, etc. The difference is that the exit instruction sign must be augmented with a tilted upward arrow pattern consistent with the direction of exit travel. The main function of the exit signs is to allow drivers to exit before the final determination of the destination, and according to the arrow direction away from the main line into the exit ramp.

Exit signs can be installed either roadside (single or double post) or overhead (gantry or single cantilever). Roadside type must be installed at the beginning of the deceleration lane, if the distance from the beginning of the deceleration lane to the exit triangle is less than 90m, it is not suitable to use the roadside type, and should be set up in front of the exit triangle at an appropriate location of the elevated exit indicator sign. When there are more than one exit in the same direction of the interchange, it is suitable to set up elevated signs, the exit indicator sign of the first exit and the exit warning sign of the second exit are set up side by side on the same bracket, and pay attention to correspond to the arrangement of the lanes on the road.