Capacity

One key to building a successful ski area is to achieve to optimum balance between slope capacity, lift capacity, utilization and lift ticket prices. It costs an average of $438 per skier to provide uphill transportation and $125 per skier to construct slopes and trails. The ski area designer’s objective to provide the optimum balance that will attract and satisfy skiers, while also meeting the ski area operator’s financial goals. A current additional concern is to preserve the quality of the skiing experience, while continuing to meet an explosive demand of skiing opportunities.

The concept of a ski area’s balanced capacity is receiving new attention. U.S. ski areas on public lands are required to measure capacity and utilization as an indication of competitiveness. The mountain’s skier capacity is also critical to community planners, transportation planners and environmental impact analyses.

The capacities ski slopes and ski lifts are matters of judgement. However, there are planning parameters, and there is a logical planning process to assist designers and ski area developers in reaching reasonable judgements. Conceptually, acceptable area capacity is a function of the skier’s skill, physical condition, tolerance of crowds and alternative choices. More practically, area capacity is a function of the terrain, its steepness, design characteristics, the quality and quantity of snowcover and the extent of snow grooming.

Specifically slope capacity is measured in number of skiers per acre. Acceptable densities are lowest in the Rockies at vacation destination resorts where there is an abundance of terrain; and highest at metropolitan day/night ski areas in mid-America where hills are scarce, and even created by massive earthmoving.

Lift capacity is measured in vertical transport feet per hour. Skier demand varies greatly from extremely low for timid, first time skiers to extremely high for a physically strong, experienced, expert skier.

The accompanying tables represent a range of judgements. How do you select the proper criteria for your ski area?

Design Capacity

The comfortable, acceptable or “design-skier” capacity of any site or ski area is limited by one or more natural, unalterable physical characteristics. The ski area balanced design capacity is thus limited to the capacity capability of the constraining barrier. Potential constraints to capacity are:

1. Mountain terrain capacity
2. Access road capacity
3. Parking area capacity
4. Water capacity
5. Airport capacity
6. Environmental capacity

Thus, the first procedural step in determining design capacity is to evaluate these potential constraints to identify the probable controlling factor. Generally, the potential mountain terrain capacity will limit the size of ski areas east of the Rockies, whereas more and more the potential environmental impact becomes the key factor at western sites.

The terrain capacity decision, the second step in determining design capacity, involves a judgement concerning the level of crowding acceptable. Acceptability in turn varies according to the skill of the skier, the condition of the snow surface, the type of ski area and perhaps most noticeably, the geographic location. Terrain capacity calculations include an allowance for skiers on the slopes, riding the lifts, standing in ski lift lines and resting in the base or summit facilities. Various models have been constructed ranging from my attempt to model the observed satisfaction of skiers at all types of areas; to measurements of speed variations by planners at Mammoth Mountain;¹ to observations on 10 Pacific Northwest ski areas as reported by Roland Emetaz;² to specific design goals as established by Aspen/Snowmass planner, Larry Beidleman;³ and even to precise engineering analysis, based on social distance factors, speeds, safety factors and unimpeded motion models as researched and reported by Beat von Allmen.⁴ All models attempt to justify an ideal density. However, because all models contain a judgement concerning the optimum or minimum level of congestion or tolerable spacing interval, the ultimate recommendation rests on the researcher’s concept of “acceptable” crowding. It is interesting to note, however, that all models generally agree, that acceptable densities decrease as skill levels and speeds increase. Also, as the accompanying chart illustrates, most authorities agree on acceptable densities for the intermediate to expert slopes, but there is a wide range of variance as to the density acceptable in the beginner and novice categories.

The accompanying chart plots the various “acceptable” skier slope and trail density per acre, as summarized by the before mentioned authorities. Total design capacity, or design density is some 2.5 to 5 times this figure. Table #2 illustrates two assumptions concerning where the capacity crowd may be located at any given moment. My standard minimum model limits average ski terrain density to 10.1 per acre, and results in an average design density of 19/acre. The Mammoth model, the result of formal observational research, recommends a much lower average of 4.4 skiers per acre of terrain, but results in a similar average design density (i.e., 19/acre). The major difference is in the assumptions made for the proportion of the average crowd that are inactive at any given time. Also, where most authorities base acceptability on 10 to 15 minute ski lift lines, my requirement for acceptability involves a wait equal to the time it takes to ride up. Therefore, a long lift with an 18 minute ride (2,000′ of vertical) can justify an 18 minute wait, but a five minute ride (450′ of vertical) cannot justify a 10 minute wait.

One of the problems in applying rigid research methods is that weather and snow conditions will shift these proportions drastically. For example, a freshly groomed slope with a two to five foot base of machine snow will comfortably accommodate both higher densities and lower ability level skiers, than the same slope with ungroomed moguls, and bare spots.

These parameters — skiers-per-acre as outlined on Table #1 — have survived the test of time, and if used with judgement, will preserve the quality of the skiing.

Proper ski area design provides a balance in terrain in keeping with the breakdown in skier market expectations. Thus, if the market is distributed in a normal bell curve manner, the terrain breakdown will be as follows:

	Skier Market Proportion	Skiers	Density	Acres	Terrain Proportion
Beginner	5%	50	50/Ac	1.0	2%
Novice	10%	100	40/Ac	2.5	5%
Low Inter.	20%	200	30/Ac	6.7	13%
Intermediate	30%	300	20/Ac	15.0	28%
Adv. Inter.	20%	200	15/Ac	13.3	25%
Advanced	10%	100	10/Ac	10.0	19%
Expert	5%	50	10/Ac	5.0	9%
TOTAL	100%	1,000	18.7/Ac	53.5	100%

One final observation concerns the effect of high utilization (i.e., actual skier visits divided by capacity for skier visits). Ski areas are increasingly experiencing higher utilization, and therefore, wearing out snow surfaces to a greater extent. Designers must either plan for lower average densities, or for expensive machine snowmaking to preserve the skiability of the snow surface. This new high average use factor may dictate lower densities where terrain is available, and thus these parameters are continually subject to revision when research uncovers new evidence.

Uphill Capacity

The third step in balancing ski area facilities involves the decisions on lift selection. The number and location of the ski lifts is generally controlled by the location, developed acreage and design capacity of the ski slope and trail systems. Because the quality and quantity of downhill skiing is the experience sought by the skiers, the ski lifts are only service vehicles and must therefore be located and sized to meet the downhill needs of the crowd.

The decision on uphill capacity needs is less judgemental. Research on crowds, lift lines and uphill capacity has developed some standard parameters. Table #3 summarizes my current parameters, based upon an analysis of ski area operator perceptions of what constitutes a comfortable crowd and acceptable ski lift line-ups. Again, average demand varies substantially between geographic sections. Uphill capacity is typically measured in vertical transport feet per hour (VTF/hr), the product of a ski lift’s vertical rise and its rated hourly capacity. Therefore, in developing demand parameters, I also measure skier satisfaction in VTH/hr received.

Ski area operators across North America estimated their comfortable crowds in two annual economic studies. These estimates have been related to available VTF/hr to arrive at the following average VTF/hr demand (Table #3 parameters are based on these findings).

Ski Season	1975/76 VTF/hr	1976/77 VTF/hr
Nat’l Average	1,473	1,544
New England	1,589	1,580
East	1,264	1,143
Midwest	822	1,129
Rockies	1,721	1,863
West	1,576	1,642

Using these parameters, the quantity of uphill capacity required is easily determined by multiplying the design capacity by the average VTF/demand. The final step involves some additional judgement because lift capacity is fairly standard at 1,200 people, 1,800 people or 2,400 people per hour. However, an example will serve to illustrate the procedure involved:

1. Requirement: Select the optimum lift to serve a ski area with terrain limitations as follows:
   A) Terrain capacity – 1,500 skiers (balanced)
   B) Vertical drop – Main Slopes 1,000′
   Beginner slopes 50′
2. Calculations:
   A) Total VTF/hr required equals 2,325,000.
   (1,500 skiers x 1,550 VTF/hr demand)
   B) Beginner VTF/hr required equals 30,000.
   (5% of 1,500 – 75 x 400 VTF/hr demand)
   C) Beginner lift uphill requirement is 600/hr.
   (30,000 VTF/hr – 50′ vertical)
   D) Total remaining lift uphill requirement is 2,295/hr.
   (2,295,000 VTF/hr – 1,000′ vertical)
3. Proposed Lifts: Depending upon the points to be served, this ski area will required two 1,200/hr double chairs, or one double/double, and one small platter or wire rope for the beginners.

Of course, the principal can be applied equally at a major resort where large capacities and many lift systems are contemplated. For example, lifts may be tailored to specific terrain as follows:

Terrain Type	Skier Capacity	Skier Demand (per hr.)	VTF/hr Demand (000)	Vertical Rise	Required Uphill Capacity
Low Inter.	1,200	1,200	1,440	800′	1,800/hr
Expert	600	3,000	1,800	1500′	1,200/hr
Novice	2,000	900	1,800	750′	2,400/hr

Additional calculations may be required where the developer seeks to appeal to a specific market segment. Tables #1 and 3 parameters may be utilized to balance an area that is skewed to high or low ability levels by rearranging the skill mix proportions and calculating required downhill acreage and uphill capacity.

These parameters provide acceptable ski industry guide lines. They must also meet the test of economics. The more costly it is to provide the skiing surface (such as earthmoving and snowmaking), the greater the density acceptable, and the lower the average vertical provided. The procedure outlined provides a logical method of applying judgements, yet still maintaining standards that have survived the test of time in the market place.

REFERENCES

1. Mammoth Mountains, Winter Recreation Master Plan Alternatives; O’Connor & Associates; 1978, pps 17-19.
2. Winter Sports Site Base Area Study; PNW Region USFS; Walters, Henley & Emetaz, 1970.
3. Mountain Capacities – Snowmass Skiing Corporation; Larry Beidleman, February 1973.
4. How to Measure and Rectify Ski Area Crowding; Beat von Allmen P.E., Ing. HTL; Internationale Seilbahn-Rundschau/Technik in Winter.