Storm after winter storm, snow piles up deeper and deeper, 20 feet (6m) or more on some snowmobile and cross-country ski trails. Trail signs are normally mounted at a set height on a post planted in the ground. Once the snow has piled up over the sign, the sign is no longer effective.
Ranger Districts with winter trails programs have been dealing with the problems of signing snow trails for as long as they have managed winter trails. The Missoula Technology and Development Center (MTDC) asked snow trail managers to tell us how they keep their winter trail signs visible. We also developed some prototype signposts that we thought might work in all snow depths. The prototypes worked, but were too cumbersome and costly for us to recommend, except in special situations.
This report describes signpost systems that work best in shallow, moderate, and deep snowpacks. Traditional signposts, anchored firmly in the ground, work best for trails with moderate and low amounts of snow. Free-floating signposts, supported only by the snow around them, work best in moderate and deep snowpacks. Telescoping signposts and signposts with temporary bases work for shallow, moderate, and deep snowpacks. However, these signposts are more expensive and take more work to install and maintain than traditional or free-floating signposts. The method of driving a steel fencepost or metal pipe into the ground as a temporary support for a tubular plastic signpost is regarded by the Center as an unacceptable safety hazard.
Need for Snow Trail Signing
Designated National Forest snowmobile and cross-country ski trails require signing that is consistent with the purpose of the trail, Forest Service policy, the recreation opportunity spectrum, safety, and Forest Plan direction. These should be spelled out in a written sign plan for the trail system. An individual engineering study, called a sign warrant, is required for regulatory and warning signs.
Verify your written sign plan in the field before you implement it. This will ensure that the right signs end up at the right places. Relying solely on an office-generated sign plan will usually result in unnecessary and inappropriate signs.
Standards for Forest Service Signs and Posters (EM-7100-15) covers all types of signage. Before purchasing or installing any cross-country ski or snowmobile trail signs, review this publication, especially Chapter 5, for sound advice and policy requirements. You should be able to borrow a review copy from your Forest Service sign coordinator.
Some states also have guidelines for snowmobile trail signing. Many of these are based on the International Association of Snowmobile Administrators' Guidelines for Snowmobile Trail Signing.
Importance of Placement
Placement is often the criteria that determines whether a particular sign will be effective. This is especially critical for winter signing when visibility can be at its worst. Signs should be clearly visible. You may be installing signs on a warm, clear day. But you should position your sign with the unfamiliar user, blowing snow, and fog in mind. Do not rely on travelers following tracks. Assume the tracks have been obliterated.
Mount signs 2 to 6 feet (610 mm to 1.8 m) from the right edge of the trail tread to the nearest edge of the sign to provide adequate clearance (Figure 1).
Figure 1-Signs should be mounted at least 40 inches (1 m)
above the average maximum snow level at the bottom of the
sign. Signs placed more than 8.5 feet (2.6 m) above the
snow level may not be visible, especially at night.
To keep signs free of snow and ice and to increase visibility, place signs where they will be protected from the prevailing wind, if possible. Reassurance blazers (Figure 2) on trees should be mounted with nail heads exposed. The blazer should be placed halfway between the nail head and the face of the tree to allow it to flex in the wind.
Figure 2-The Hebgen Ranger District at West
Yellowstone, Montana, uses 2 by 2's with 5-inch by 7-inch
(127-mm by 178-mm) blazers as reassurance markers.
When blazers are mounted on trees, prune limbs well above the sign so that snow-covered limbs will not droop and obscure the sign.
Snow Trail Signpost Evaluations
Snow trail managers told MTDC that only a few signposts had passed the test of time. In addition, some nontraditional products, such as telescoping steel signposts and polyvinyl chloride (PVC) plastic pipe, have been effective. All the signpost systems used in the field are simple, inexpensive, and effective (Figure 3).
Figure 3-Minus zero: Icy nuts dropping into the snow.
Signposts frozen in solid. High winds and poor visibility. Oops!
There goes the wrench! Good reasons to keep your signpost system simple.
Choosing the best signpost depends on the expected snow depth. Trail managers commonly use two or three different types of signposts based on the expected snow depths in particular parts of the trail system.
Table 1 summarizes our findings. Extra-high, fixed-base signposts permanently set in the ground worked best in shallow (0 to 3 feet, 0 to 1 m) and moderate (3 to 12 feet, 1 to 3.7 m) snowpacks. Free-floating signposts of wood or PVC that were supported only by the snow worked best in moderate and deep (more than 12 feet, more than 3.7 m) snowpacks. Temporary bases and telescoping signposts worked for shallow, moderate, and deep snowpacks. They were seldom used because they required more maintenance, were more expensive, or presented unacceptable hazards.
||Works best at (snow level)
||Description and Comments|
||Install longer-than-normal posts with holes drilled so the sign can be raised|
||Post can be telescoped as depth increases, or better yet, sign can be raised or lowered.|
|Buried steel base
||4 by 4 can be fastened to base|
|Double posts with rungs
||An option for bulletin boards or other heavy signs|
||Inexpensive and lightweight-can be painted|
||Square for easier sign mounting, more expensive, and shorter than PVC pipe|
|2 by 2, or 2 by 4
wooden native poles
||Simple, inexpensive, and popular for reassurance markers and small signs|
|Temporary Base and Telescoping|
|Wooden base with
2 by 4 signpost
||Will need to be able to pull the posts out of the base for deep snow|
|Portable steel base
with PVC signpost
||Will not need to be able to pull out of base for deep snow|
|Steel base with steel
signpost with telescoping
||Worked, but too expensive|
|Steel fenceposts or
conduit pipe base
||Created unacceptable hazard-not recommended|
Traditional wooden signposts anchored in the ground were the most common signposts. They work fine in areas of low and moderate snowfall, even though the sign may end up less than the recommended 40 inches (1 m) above the snow (Figure 4).
This sign has just about lost its effectiveness.
Anticipating the amount of snow accumulation allows trail managers to customize their fixed signposts. For example, in areas with low to moderate snowfall, a standard summer-use sign height may be satisfactory for winter. Or a post two feet (610 mm) taller than normal might be good for year-round use.
For deeper snow, a much taller fixed wooden signpost may be needed. Signposts up to 16 feet (4.9 m) long can have a number of mounting holes that allow workers to move the sign up and down (Figure 5).
Figure 5-AFTER: Raising the sign to a
higher set of holes makes it effective once again. Some
Districts use permanently set signposts up to 16 feet (4.9 m)
tall with holes drilled at several levels.
Another variation is to bolt post extensions onto existing signposts. The extensions should be bolted on before heavy snowfall to avoid having to dig out the top of the post. Metal braces can be used to help support larger signs (Figure 6).
Figure 6-Metal braces can strengthen sign supports on larger signs.
For holding heavy bulletin boards, the Deschutes National Forest built a ladder-like, double-post frame. The bulletin board hangs from one of the ladder rungs (Figure 7). The 4- by 4-inch posts shown in the photo were not strong enough, so they were replaced with peeled 8-inch (200-mm) logs.
Figure 7-Simplicity itself. Hooks on the back allow the bulletin board to be moved from one
rung to the next. Hooks are much easier to work with than nuts and bolts. Two people can
easily lift the bulletin board to the next rung. Supplemental security bolts or a lock and chain
could be added in areas where users tend to evaluate signage by its warming fire potential.
Steel signposts (Figure 8) are popular in areas where a sturdy post is required. They work best for low to moderate snow depths. These signposts, designed for highway signing, are made by several manufacturers. They offer the convenience of a permanent base embedded in the ground, and they have adjustable, removable steel posts for mounting the sign.
Figure 8-Steel signposts are quite popular at plowed snowparks where
signposts need to withstand the force of plowed or blown snow.
The steel posts come in a variety of lengths and dimensions. A 15-foot (4.6-m), 2- by 2-inch (50- by 50-mm) steel post would be long enough for most areas. The sign could be raised and lowered as needed.
Tubular steel posts can be telescoped with posts of the next larger or smaller size. Because of their relatively tight fit and the tendency of the bolts and steel members to freeze together (and the need to dig out part of the buried post for adjustments), few managers prefer telescoping signposts. It is easier and less expensive to simply move the sign to another set of holes on a fixed signpost.
The steel posts are heavy, so freight costs and the logistics of getting them to the site are important considerations. The underground bases need to be installed before the ground is frozen. The steel signposts are more expensive than most wooden ones. Costs vary too much nationwide to provide a good comparison here.
In deep snow, signposts supported only by snow work best. In every deep-snow situation, this was the technique crews used, and it is the technique we recommend. Signposts supported only by snow also work well for moderate snow levels.
The Payette National Forest mounts signs on 2 by 4's (50 by 100 mm) tamped into the snow. Other Forests and Districts use 2 by 2's (50 by 50 mm) for the same purpose, placing them next to nearly buried signposts in some instances (Figure 9). The 2 by 2's have a tendency to freeze in place in wet snow and are difficult to raise without breaking. Another option for reassurance markers is native 12-foot (3.7-m) poles. During periods of unexpected heavy snowpacks, Districts may stick temporary wooden signposts in the snow on top of buried fixed signposts. All of these signposts are relatively inexpensive.
Figure 9-Standard 2 by 2's or native poles are inexpensive
and effective ways to place reassurance markers. They freeze in
pretty solidly, however, and are difficult to raise without breaking.
PVC Pipe Signposts
The Deschutes National Forest signs many miles of winter trails and posts wilderness boundaries to prohibit motorized entry. The signposts that work best are 10-foot (3-m) sections of 2-inch (51-mm) and 2½ (63.5-mm) Schedule 40 PVC pipe (Figure 10 and Figure 11). On the boundary of the Three Sisters Wilderness, these signposts are exposed to rime, ice, heavy snow, winds of up to 80 miles per hour (128 kilometers per hour), and temperatures as low as -20 1/2F (-29 1/2C). Signs are placed early in the season in at least 3 feet (1 m) of snow, then raised four to six times during the course of the winter as snow piles up.
Figure 10-PVC pipe has worked best to post the
Three Sisters Wilderness boundary. The upper two-thirds
of the pipe is painted orange to improve visibility.
Figure 11-A wooden block inside the round PVC pipe allows signs to be
mounted securely. Drill holes perpendicular to the grain to prevent the wood from
splitting. Then screw the lag bolts into the wood.
Two inexpensive products to consider for snow trail signposts are white PVC Schedule 40 water line and gray PVC Schedule 40 electrical conduit. We saw the white pipe being used for signposts in the field. The gray pipe has ultraviolet (UV) inhibitors that provide some degree of resistance to degradation by sunlight and might work better. It costs about the same as the white pipe.
To improve visibility, you will probably want to paint the part of the PVC pipe that extends above the snow. Do not paint the whole pipe, because you want the part buried in the snow to be as slippery as possible. Paint doesn't stick to untreated PVC, so our local paint store suggested scuff sanding to prepare the surface, then painting with polyurethane enamel. We did not have time to verify how well this works (Figure 12 and Figure 13).
Figure 12-Two PVC pipes hold this large sign in place. Because
the posts are not anchored to the ground, they can be
raised as the snow becomes deeper.
Figure 13-Reflectorized tape
greatly improves the sign's visibility at night.
PVC pipe becomes brittle at very cold temperatures and after long exposure to sunlight. Painting may help protect it from sunlight. How long will the pipe last in the field? The Bend/Fort Rock Ranger District on the Deschutes National Forest reported increased ice and snow buildup during the third season of use, making the PVC posts more difficult to lift. This could be due to the degradation of the PVC. Perhaps it could be temporarily fixed by waxing the lower part of the post. In this instance, the white pipe was used instead of the gray, UV-resistant pipe.
The Bend/Fort Rock Ranger District also tried 5- by 5-inch (125- by 125-mm) polyvinyl fenceposts placed in the snow. The square fencepost provides a flat surface for attaching the sign. The posts are available from several manufacturers. Even though the posts (Figure 14) are much more expensive than PVC pipe ($13.25 for a 6.5-foot (2-m) post), they are not long enough for many snow installations.
Figure 14-Plastic fenceposts make effective
signposts, but are much more expensive than round PVC pipe.
What should you do in situations where there isn't enough snow to support a freestanding sign, but you don't really want a permanent signpost?
One option is to use a permanent signpost anyway. You can always remove or cover the sign during the off season, or install a hinged sign that can be folded over when it is not being used.
Another option is to remove the signposts seasonally. MTDC looked at several techniques for temporarily mounting a signpost.
We find this design unacceptable because the steel index rods present an unacceptable hazard to snowmobilers or skiers who may run into them. What seems like a safe, out-of-the-way signpost location may look like the middle of the trail after several feet of snow have fallen. And, when it is time to remove the seasonal snow trail signs, the index rods are probably still frozen in the ground and cannot be removed, leaving these hazards for the summer season.
Because of the safety hazard, we do not recommend using short, narrow support rods like steel fence posts or conduit that are driven into the ground to support signs or signposts.
Square Plastic Signposts Supported by Steel Rods
Kirk Metzger on the Sisters Ranger District, Deschutes National Forest, experimented with 10-foot (3-m) long, 3-inch (76-mm) square plastic downspouts placed over steel index rods.
He drove a 6-foot (1.8-m) fence post, scrap pipe, or 2-inch (51-mm) diameter electrical metal conduit into the ground with a post driver. The metal pipe supported the signpost when the snowpack was shallow.
He attached a sign to a 10-foot (3-m) long, 3-inch (76-mm)-square section of plastic downspout and slid the downspout over the index rod. The plastic downspout could be raised as the snow got deeper.
Kirk found that the plastic gutters are not very strong and they shatter in high wind and extreme cold. Stronger square tubular materials, like 4- by 4-inch (100- by 100-mm) PVC fence posts or round PVC pipe would work better.
Buried Steel Brackets
Square tubular steel signposts can be mounted on a bracket driven into the ground. When the steel signpost is removed, the mounting frame is only a few inches off the ground. The signpost can be removed in the spring and reinstalled in the fall. This assumes that you can find the mounting bracket in the spring, and that you install the signpost before it is covered with snow and ice each fall. Such a signpost is best suited for plowed parking lots and junctions where it will be easy to find.
The Crescent Ranger District on the Deschutes National Forest drives 4-foot-(1.2-m)-long pieces of 4- by 4-inch (100- by 100-mm) steel tubing into the ground, leaving 6 to 8 inches (150 to 200 mm) exposed. All but 18 inches (450 mm) of the tube is filled with gravel for drainage. Wooden signposts (4 inches by 4 inches) are placed in the buried tubing during the winter and removed in summer. The tubing needs to be covered with a metal cap or duct tape during the off season to keep it from filling with dirt.
One District mounts its signs on 10-foot (3-m), 4- by 4-inch (100- by 100-mm) posts with cross braces at the bottom, and sometimes uses sandbags for extra support in windy areas.
They are set in 2 feet (610 mm) of snow initially. When they need to be raised, volunteers dig them out, presumably bases and all, and reset them.
Another portable sign mounting base was developed by Gary Weigel when he worked on the Shoshone National Forest. These steel bases (Figure 15) are relatively easy to fabricate and can be customized to fit the type and size of signpost you are using. They can be pinned to the ground for better support.
Figure 15-Gary Weigel designed this portable base. It is easily fabricated and can
be customized to fit round or square posts. This base was used for MTDC's telescoping PVC
signpost system (on top), and also for the square tubular steel and Extren signpost (on bottom).
The signposts can be permanently attached to the base or left unbolted so that the posts can be pulled out to raise the sign. The signpost may freeze to the base, making it immovable.
The bases need to be removed in the spring after the ground has thawed. Locating and transporting the heavy bases after all the snow had melted created enough extra work that one District discontinued using them.
Why not develop a telescoping signpost that could be raised as snow depths increase? This would allow a single signpost to serve for shallow, moderate, and deep snowpacks.
MTDC looked at three such systems. One is commercially available and the other two were prototypes constructed in our shop.
Telescoping square tubular steel signposts are commercially available. They can be detached from bases driven nearly flush with the ground. They work quite well for many situations.
To reduce weight and reduce the likelihood that close-fitting steel posts may freeze together, MTDC telescoped a 2-inch (51-mm)-square plastic tube onto a square tubular steel post. It was mounted with quick-release fasteners rather than nuts and bolts (Figure 16). In limited field testing, the unit held up well and did not freeze. Extren, the industrial-strength plastic we used, costs nearly $5.00 per foot. It is far too expensive for us to recommend as an alternative to less expensive signposts that are easier to install.
Figure 16-MTDC's steel and Extren plastic telescoping signpost system. The Extren plastic
cost too much for us to recommend this system even through it is satisfactory
otherwise. Telescoping two pieces of steel tubing is less costly.
MTDC also telescoped two lengths of 1 1/2-inch (38-mm) and 2-inch (51-mm) Schedule 40 PVC pipe (Figure 17). This also worked, although we do not know how sturdy this would be on sideslope installations, where snow continually migrates downhill and would bend the signpost.
Figure 17-The top of MTDC's telescoping PVC signpost. It was
difficult to line up the holes drilled through the PVC, and who wants to
dig down this far to reach the buried fastener, anyway?
If you really need a system that is anchored to the ground, the telescoping PVC signposts might work. We did not see our field testers clamoring to use them instead of permanent signposts or free-floating signposts-methods they recognized as simpler, easier to maintain, and cheaper.
Additional single copies of this document may be ordered from:
USDA Forest Service, MTDC
5785 Highway 10 West
Missoula, MT 59808
Phone: (406) 329-3900
Fax: (406) 329-3719
For further technical information,
contact Brian Vachowski at the address above.
Phone: (406) 329-3935
Fax: (406) 329-3719
Lotus Notes: Brian Vachowski/WO/USDAFS
For more information, visit the US Department of transportation's Forest Service Publications