ARE 5.0 PPD · Complete public sample

Convert site slope into the horizontal space it needs

Read percent slope as a ratio and check whether a route can fit the site's supplied constraints.

Understand the governing concept.

Percent slope is 100 times rise divided by horizontal run. Match the units first, then solve for the missing geometric quantity. A small percentage can require a long route when the change in elevation is substantial; multiplying rise by the percentage reverses the relationship.

Use the calculation as a feasibility screen, then incorporate the actual route, landings and site obstructions. The horizontal run is not the diagonal distance along the sloping surface. If the available corridor is too short, a different route or coordinated elevation change is needed before detailing the solution.

By the end of this refresher

Explain the basis or assumption controlling this decision.
Apply the method within its stated limits.
Check the result and choose a related study task.

S=100\frac{\Delta z}{L},\qquad L_{\min}=\frac{\Delta z}{S_{\max}/100}

Use the percent as a fraction when solving for minimum horizontal run.

Define the basis before substituting a value
Symbol	Meaning	Unit or basis
$S$	Percent slope	%
$\Delta z$	Vertical rise	ft
$L$	Horizontal run	ft
$S_{\max}$	Supplied maximum percent slope	%

When the method applies

The slope limit is a supplied hypothetical project criterion. This calculation is not a complete accessibility or site-drainage design.
The examples ignore landings, cross slope and transition lengths only because the supplied exercise defines a continuous idealized sloping segment.

An idealized continuous segment rising3ft at5percent needs60ft horizontal run; a48ft corridor is insufficient. Landings and transitions are outside this supplied exercise. — A small slope can require a long horizontal run. Use the worked-case givens and limits below. Open the diagram for a full-size view; scroll horizontally on a narrow screen.

Original teaching case

Work the decision, then cross-check it.

An idealized continuous path must rise 3 ft. The project's supplied slope limit is 5%, and the available straight horizontal corridor is 48 ft. Ignore landings and transitions for this feasibility exercise.

Express 5% as 0.05 and solve the required run: 3/0.05 = 60 ft.
Compare 60 ft with the 48 ft corridor; another 12 ft of horizontal run is needed.
Check the existing corridor directly: 3/48 × 100 = 6.25%, which exceeds the supplied limit.

L_{\min}=\frac{3}{0.05}=60\ \mathrm{ft},\qquad S_{48}=100\frac{3}{48}=6.25\%

Decision

Revise the route or elevations; the 48 ft straight corridor cannot satisfy the supplied 5% criterion.

Independent check

More run at the same rise lowers the slope. A run shorter than 60 ft must produce a slope greater than 5%.

A fresh application

Use the concept under changed conditions.

Choose a response before inspecting the reasoning. This is a learning check, separate from scored diagnostic and mock attempts.

Connect this refresher to your program.

Open related lesson PPD-L04 in owner review →
Connect this prerequisite to the complete program explanation and its conditions.
Move to related program practice →
Use new questions after focused repair; keep learning checks separate from diagnostic and mock results.

NCARB provides examination formulas, structural resources and case-study material. Refresh site response, system selection and tradeoffs before comparing design alternatives. The full PPD program is in invited development review; paid enrollment remains closed. This topic is classified as understanding and application; no individual reference omission has been verified.

Original ReasonSpan^™ teaching material. AI-assisted checks are complete; independent specialist review remains pending.