The Vehicle You Are Not Allowed to Turn Away
Every parking lot serves one vehicle it is not allowed to turn away. On a retail pad that is usually the refuse truck. At a medical office it may be the ambulance that has to reach the canopy. Behind a distribution building it is the tractor-trailer at the dock, and on nearly every site the fire apparatus holds a claim the fire marshal will enforce whether or not anyone drew it. Passenger cars govern almost nothing.
Ask the owner who actually shows up and how often. Hauler, linen service, fuel drop, the box truck that restocks twice a week, the tow truck that will eventually recover a car from the back row. Each has a wheelbase, a lock angle and a minimum turning path. The largest of them that cannot be refused becomes the design vehicle, and its swept path becomes the skeleton the rest of the lot hangs on.
AASHTO's A Policy on Geometric Design of Highways and Streets publishes standard design vehicle classes together with their minimum turning paths. Work from the published template for the class you named, not from a radius somebody remembers from the last job. Where a fire apparatus governs, the local fire authority will usually name the apparatus and hand you its turning data on request.
Getting this wrong is expensive in a quiet way. A lot laid out on car geometry looks finished until the hauler arrives and discovers he has to reverse a hundred feet down a two-way aisle to reach the enclosure. The owner then pays for smaller trucks at higher frequency for the life of the building, or pays to cut out a curb line that was poured a season earlier.
Two Envelopes: Tyre Path and Body Swing
A turning template draws two outlines and they are not the same. Rear tyres off-track to the inside of the front tyres, so the tyre path pinches in through the turn. The front overhang swings the other way, outside the front tyres, wider than anything on the ground. Tyre path is what shears an island nose and crumbles an unsupported pavement edge. Body envelope is what takes a mirror off a light pole or catches a canopy column.
Templates also assume a driver at full lock, at crawl speed, who knows the lot. Real drivers arrive at night, in rain, loaded, with a car parked where it should not be. Carry a clearance margin around both envelopes; a foot or more on each side is common, and some jurisdictions specify the margin for apparatus access routes. Where nothing governs, settle the margin with the owner in writing rather than discovering it later in the pavement.
Draw the envelopes before you draw a single stall. Overlay them at every place the vehicle changes direction: the street apron, each aisle-to-aisle junction, the dock or enclosure approach, and the turnaround at the end of every dead-end run. Whatever plan area survives those overlays is the parking field. Nothing else is.
Aisle Width Falls Out of the Turn
Stall angle and aisle width trade against each other, and that trade is settled by the turn rather than by the stall. Ninety-degree stalls give the tightest module per car and allow two-way circulation, but a driver needs the deepest aisle to swing in and back out square. Angled stalls at sixty or forty-five degrees ease the turn-in and let the aisle narrow, paid for with one-way circulation, wasted triangles at the ends of rows, and fewer cars per acre.
Run the sequence backwards from the way it is usually taught. Fix the aisle the design vehicle needs to complete its turn without crossing an opposing lane or riding a curb, then find which stall angle that aisle will carry. On a site where a single-unit truck must turn out of a parking aisle into a drive lane, the aisle dimension is already decided; stall angle is simply whatever fits inside it.
Stall width and depth minima are jurisdictional. The zoning ordinance or parking code adopted by the municipality governs, and many distinguish between standard, compact and employee stalls, sometimes capping the share of compact spaces. Confirm the adopted edition and any local amendments before layout. A field striped to the wrong minimum comes out and goes back in at the contractor's cost, and the second striping never quite hides the first.
With the aisle already fixed by the design vehicle's turn, this is the point at which stall angle, stall depth and module width have to be reconciled against one another rather than assumed.
The total length of the parking row available for stalls, excluding curbs, aisles, or obstructions.
The width of a single standard parking stall.
Parking stalls per row
21 stalls
They open the calculator with your figures already in it
Parking Lot Stall Layout Calculator: 21 stalls — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- Assumes the stalls sit square to the row. Angle the parking and each stall's bite out of the row length becomes the stall width divided by the sine of the angle - a 2.7 m (9 ft) stall consumes about 3.1 m (10.2 ft) at 60 degrees and about 3.8 m (12.7 ft) at 45 - so the same row holds roughly a seventh fewer stalls at 60 degrees and a third fewer at 45. The trade is a narrower drive aisle and one-way flow, so the count and the aisle have to be decided together rather than one after the other.
- The end stalls are not standard stalls. A stall running against a wall, a fence, a column or a raised landscape curb loses the door swing it would otherwise share with its neighbour, and site standards commonly widen it by about 0.3 m (1 ft) for exactly that reason, while a column inside a parking structure encroaches further again. Two widened ends are often the whole difference between the number here and the number that gets striped.
Testing the Count Against What Is Left
Reservations for swept path are not negotiable, which makes the stall count a residual rather than a target. Take out the turning envelopes, the turnaround bays, the enclosure approach and the fire lane, then the landscape islands the ordinance requires, then somewhere to push snow in climates that get it, then whatever the stormwater practice occupies at grade. Count the field that remains.
Two numbers have to meet. The required count comes from the zoning ordinance, usually as a ratio to floor area, seats, beds or keys, and the owner's own operating experience or a demand reference such as ITE's Parking Generation may argue for more. The achievable count comes from the geometry after reservations. If those two numbers do not meet, something structural has to move — the building footprint, the design vehicle's route, the number of access points — and that is a decision for the design table, not for the striping crew.
Test it early, while the plan is still cheap to change. A count that fails after engineering has been paid for is a redesign; a count that fails during layout is a variance application with a hearing date months out.
Once the swept paths, islands and turnaround bays are reserved, the count the remaining field can still deliver has to be checked against the count the ordinance demands, before the plan goes to engineering.
The length of the parking area, along which stalls line up side by side.
The width of the parking area, across which stall rows and drive aisles stack.
Estimated stall count
84 stalls
This is a rough site-planning estimate using a simple rectangular double-loaded layout — actual capacity depends on your specific lot shape, ADA-accessible stall requirements, landscaping islands, one-way vs two-way aisles, and local zoning code minimums, which a civil engineer or site planner accounts for in a real design.
- Stalls per row
- 21 stalls
- Double-loaded row pairs
- 2 pairs
They open the calculator with your figures already in it
Parking Lot Size Calculator: 84 stalls — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- The last line of the arithmetic multiplies by two, so every band of width is credited with a full row of stalls on both faces of its aisle and the answer can only ever come out even; a row that runs against a building frontage, a fence or a retaining wall is single-loaded in reality and delivers half of what is counted here.
- Stall width, stall depth and aisle width are three fixed constants in the file with no input offered for any of them, so compact bays, a wider stall than the 9 ft (2.7 m) assumed, and 45- or 60-degree angled rows are layouts this tool has no way to express.
- Only the two plan dimensions reach the calculation, which makes the site a flat empty rectangle: a slope steep enough to force terracing, an existing tree, transformer pad or manhole in the middle of the paving, or a column grid in a covered deck all remove stalls that the count keeps.
- No term subtracts anything after the multiplication, so the furniture a finished lot carries — a dumpster enclosure, a cart corral, EV charger bollards, light-pole bases, a snow-storage corner — is still being counted as parkable stalls.
- Length and width are floored independently before they are combined, which makes the figure non-additive: an L-shaped or tapering site broken into two rectangles and run twice throws away a length remainder and a width remainder in each piece, and the two answers added together fall below what one continuous striping run across the same paving would hold.
The Apron, the Throat and the Street
The swept path starts in the street, not at the property line. A curb return that is too tight forces a truck to swing into the oncoming lane to enter, which the traffic authority will see on the plan long before a driver does. Overlay the entering and exiting envelopes across the apron, both turning directions, and check whether the body clears the far edge of the drive and the near-side sidewalk.
Throat length matters as much as radius. The stretch of drive between the street and the first parking aisle has to hold whatever queues there — cars waiting for a gate, a drive-thru tail, a truck stopped at a call box — without backing into the street or blocking the first aisle. Where a gate arm is involved, the arm must clear the longest vehicle's overhang before it drops, and the reader or call box must sit at a height a truck cab can actually reach.
Grades and cross slopes across the apron carry their own rules. The pedestrian route crossing a driveway forms part of the accessible route, and the ADA Standards for Accessible Design govern its running slope and cross slope. Long vehicles also hang up at abrupt grade breaks near the property line, so check the profile along the wheel path, not just the plan.
Dead Ends and the Back-Out Nobody Drew
Any run that does not connect to another run needs a way out for the design vehicle. A car can three-point at the end of a row given a little extra depth. A single-unit truck needs a hammerhead, a bulb, or a Y with legs long enough for its wheelbase, and a combination vehicle usually has to be kept out of dead ends altogether. The adopted fire code sets the dead-end length beyond which an apparatus turnaround becomes mandatory, along with the turnaround forms it will accept.
Refuse enclosures fail more often than anything else on a lot. The truck has to approach straight, stop square, lift, set down and pull away, and the space it needs in front of the gates runs far longer than the enclosure itself. Reserve that approach as marked no-parking pavement with a sign, because one car left in it cancels the pickup for the week. Enclosure gates that swing outward into the approach need a hold-open, or they become the thing the truck hits.
End stalls against a wall, fence or building face deserve a second look. Backing out of the last stall in a row means turning into a corner that offers no relief, and the stall that cannot be used gets used anyway, usually by scraping the wall.
Accessible Stalls Have Their Own Swept Path
Accessible stalls are governed by a swept path that belongs to the user rather than the vehicle. A side-loading van deploys a ramp or lift into the access aisle, and a wheelchair user then travels from that aisle along a route to the entrance. The ADA Standards for Accessible Design set the number of accessible and van-accessible spaces relative to the total, their dimensions, the access aisle, the vertical clearance along the van route, and the characteristics of the accessible route. State and local accessibility codes may be stricter, and where they are, they govern.
Placement is not a leftover decision. Accessible stalls belong on the shortest accessible route to the entrance served, which usually means giving up the spaces nearest the door rather than filling a corner with them. An access aisle that a drive lane crosses is worthless — a deployed ramp occupies it, and a driver approaching from behind cannot see the person on that ramp.
Slope tolerance is unforgiving here. Build the stall, the access aisle and the route below the maximum permitted slope, because paving tolerance, compaction and the transition at the gutter line all eat into whatever margin was drawn. Check the finished surface with a smart level before the striping crew arrives, and correct in the binder while correcting is still paving rather than demolition.
A smart level hands you a rise over a run and the standard states a percentage, so make that conversion standing on the stall rather than back at the trailer.
The vertical change in height over the run.
The horizontal distance over which the rise occurs.
Slope grade
8.974 %
- Angle
- 5.13 degrees
They open the calculator with your figures already in it
Slope & Grade Calculator: 8.97 % — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
What this calculation does not cover
- Run is taken as the true horizontal distance between the two ends, and nothing converts a tape laid along the sloping face into that horizontal — measure along the surface instead and the grade reads lower than the ground really is, with the gap widening as the slope steepens.
- Rise is read as a magnitude only, so a drop and a climb of the same size return the same positive grade and a negative entry is floored to zero; which end is higher stays your own note rather than something the answer carries.
- Both figures describe a single straight line drawn between the two points you measured, so any crest, dip or bench sitting between them is averaged away, and cross-fall across the width of a drive or path is not part of the arithmetic at all.
- The output covers grade percent and the matching angle; the sloping distance itself — what you would order ramp board, handrail or edging against, and always longer than the run — is not worked out, nor is the result expressed as the 1-in-X ratio that specifications are often written in.
- No ceiling is applied to the outcome: a 2% fall and a 45% bank come back with identical confidence, and the accessible-ramp and driveway grade figures quoted in the questions below are context for reading your number, not a test the calculation runs against it.
The Swept Path Has a Third Dimension
Swept path has height. A refuse truck driving through a lot needs one clearance; the same truck tipping a container needs far more, and the tip point sits exactly where a canopy, deck soffit or overhead line is most likely to be. Fire apparatus carry their own clearance requirement under the adopted fire code, and a low branch, a banner, or a drive-thru clearance bar that satisfies cars will stop the vehicle that actually matters.
Profile deserves the same attention as headroom. Long wheelbase vehicles break over at crests and drag their rear ends at sags, and abrupt transitions at ramp ends, apron lips and drainage crowns across an aisle are the usual offenders. Run the profile along the wheel path through each turn, since a crown that feels comfortable straight across can become a rack when the vehicle takes it diagonally.
Winter narrows everything. Snow pushed to the ends of rows piles up precisely at the turning points, so a lot that clears a truck in September may not clear it in February. Reserve storage bays outside the swept path, or budget for hauling snow off site and tell the owner that before the first storm rather than after.
Curbs, Islands and Overhang
Overhang is what the curb detail actually has to survive. Front bumpers extend past the tyres, so a head-in stall gives up sidewalk width behind the curb, and a walk that measures fine on the plan can end up too narrow to use once cars are parked. Where a walk sits behind stalls, either widen it by the overhang or hold the vehicle back with a wheel stop, accepting that wheel stops trip pedestrians and get destroyed by plough blades.
Island noses take the worst of the tyre path. Set the nose back from the turning tyre, give it a generous radius, and expect the first course of curb at that nose to come out and go back in if the design vehicle was underestimated. Light pole bases inside islands need to clear the body envelope, not just the tyre path; a base set to the tyre line still loses its pole to a trailer corner.
Landscape islands arrive from the ordinance rather than from the traffic engineer, so they land on the plan as obstacles rather than as design. Reconcile them against the envelopes early. Moving an island on paper is a redline; moving it after curbs are poured means saw-cutting, new base and a patch that shows for years.
Island noses, the perimeter return and every run of gutter between them come out of one truck, and the section profile settled in this heading is what fixes its volume.
The total length of the curb-and-gutter run.
The vertical height of the curb face above the gutter.
The thickness of the curb section itself.
The full width of the gutter pan, measured from the BACK of the curb across the pan — not from the curb face.
The thickness of the gutter pan slab.
Curb and gutter concrete volume
7.639 yd³
- Combined cross-sectional area
- 1.25 sq ft
They open the calculator with your figures already in it
Concrete Curb and Gutter Volume Calculator: 7.64 yd³ — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- Carries no allowance for what the ground takes. The section is placed on a trimmed subgrade, and over-excavation, a soft spot, or a trimmed line running 10 mm (0.39 in) low along the whole job all add concrete that no theoretical cross-section contains. Ordering the calculated volume for a continuous pour is how a run comes up short, and a short load part-way along a curb line leaves a cold joint that stays visible.
- The concrete only. The compacted granular base under the section, the tie bars or dowels at construction joints, and the filler at expansion joints are all taken off this same run length and are the items most often left off the order — the base course alone is often as large a volume as the concrete sitting on it.
Chalk It, Drive It, Then Cap It
Layout runs from control, not from stalls. Establish one control line — commonly the building face or the longest aisle centreline — and set the aisle centrelines off it from the swept-path geometry. Chalk stall lines from a single running tape along the row rather than measuring stall to stall, because stall-to-stall error accumulates and the loss shows up at the far end where no room remains to absorb it.
Paint the swept path on the base course. Marking envelopes and aisle centrelines on the binder takes very little time and lets the design vehicle drive the lot before anything is committed. Ask the hauler for a live run with the actual truck, loaded if possible, and watch where the driver hesitates or has to correct. Adjusting a curb line before the surface course goes down is paving; adjusting it afterwards is demolition.
Stripe on a cured, swept, dry surface and follow the adopted marking standard. The Manual on Uniform Traffic Control Devices governs markings in the public right-of-way and is commonly adopted by reference for private lots, which affects colour, width and symbol layout for accessible spaces and fire lanes. Lay the whole field out in chalk and walk it before any paint goes down, because a striping machine copies a mistake at full speed and leaves a ghost that outlives the seal coat.
Chalk the whole field first and price the paint against the linear footage that chalk produced, rather than against a stall count multiplied by somebody's rule of thumb.
The combined length of all lines to be painted.
Striping paint needed
3 gallons
Coverage assumes a standard 4 in wide line at typical thickness — wider lines, stenciled symbols, or a second coat use more paint per linear ft.
- Total line length
- 655 linear ft
They open the calculator with your figures already in it
Line Striping Paint Calculator: 3 gallons — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- A CAR PARK IS NOT A LENGTH OF LINE. The figure a striping job is quoted on is bays, arrows, hatching, disabled bay symbols and the words painted at the entrance, and each is an area rather than a run — so a total linear footage understates a real layout by a wide margin.
- The default coverage rate assumes a sprayed 100 mm (4 in) line on sound asphalt. A wider line scales it directly; a porous, weathered or unsealed surface can halve it; and a brush or roller application uses more again.
- First marking and re-marking are different quantities. Paint over an existing line covers far more readily than paint on bare asphalt, so a repaint on the same layout is not the same order.
- Coverage is a single fixed figure of 300 linear ft per gallon (24 m per litre) applied to every job, and there is no field for the surface being painted, so a bare aged asphalt lot that soaks up the first pass and a freshly sealcoated one that holds the paint on top are quoted exactly the same.
- The take-off stays entirely with you, because the arithmetic reads one number and one only: a stripe left out of your tally, the line shared between two adjacent stalls measured twice, or a curbed island paced out as straight run all reach the gallon figure unchallenged.
- Rounding up to the next whole gallon is the only padding in the answer, so nothing is set aside for the paint sitting in the hose, pump and tank of an airless striper, for the waste at the start and stop of each pass, or for going back over a stripe that wandered.
- What comes back is a count of whole gallons rather than a count of containers, and the one breakdown line simply restates your footage, so nothing on the page reveals whether that final gallon is nearly spent or barely opened when you choose between 1 gallon cans and 5 gallon pails.
- Line length is capped at 5,000 m, roughly 16,400 linear ft, so a larger lot or a road contract has to be entered as separate runs, and each run is rounded up to its own whole gallon rather than sharing the leftovers with the others.
On the ground before the first line goes down
Layout for a car park is settled by the swept path of the vehicle that cannot be refused, so the takeoff starts with the turning data and ends with a live drive-through before the surface course is placed.
- Design vehicle turning template — Plotted at layout scale for the class you named, with the tyre path and the body envelope shown separately.
- Marking paint for the base course — Enough to paint turning envelopes and aisle centrelines on the binder and drive them before the top lift.
- Control line and one running tape — Stall lines chalked off a single running dimension so error does not accumulate down the row.
- Adopted fire code and zoning ordinance — Local editions and amendments govern apparatus access, dead-end turnarounds, stall minima, required count and landscape islands.
- Smart level for accessible areas — Verify running and cross slopes on stalls, access aisles and routes in the binder, while a correction is still paving.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.