16-Civ-B6 Urban and Regional Planning · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format. 16-Civ-B6 Urban and Regional Planning, National Examinations, May 2018. Three hours, closed book, calculator permitted but no calculation is set. Part A: Questions 1 and 2, both compulsory, 25 marks each, three sub-parts each. Part B: Questions 3–10 at 10 marks each, of which five are to be answered. A complete paper is therefore 100 marks. Note 6 on the front page states that most questions require an essay answer and that “Clarify [sic] and organization of the answer are important” (the printed paper reads “Clarify” where “clarity” is plainly intended) — structure and argument are marked here, not arithmetic.
Check — scope and assumptions. The Part B header prints “ANSWER FIVE (5) OF THE FOLLOWING SEVEN (7) QUESTIONS” but eight questions (3–10) are actually printed on pages 3 and 4. Front-page Note 4 governs and is the consistent reading: the first two questions plus any five of the remainder. All ten questions are answered in full below because this document is a study resource rather than a submitted script; Question 6 likewise defines all eight listed terms rather than the five asked, and Question 7 discusses all six listed subjects rather than two. Questions 1 and 2 give a scenario but no engineering data, so where a quantity is used to make an argument concrete it is introduced as an explicitly stated assumption — permitted, and indeed invited, by front-page Note 1. The paper uses Ontario’s vocabulary (“Official Plan”, “minor variance”, “site plan control”), so Ontario’s Planning Act is cited as the primary statute with the British Columbia Local Government Act equivalent given alongside; the answers stay in the Canadian frame throughout.
Reference texts for 16-Civ-B6.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Given. A typical suburban neighbourhood plan of 100 hectares gross, containing 1,300 dwelling units, in which 25 hectares are road rights-of-way and 10 hectares are park, school and stormwater management blocks, leaving 65 hectares in residential lots.
Find. The gross and net residential densities, and the reason the two differ.
Both measures are dwelling units (or people, or rooms, or bedrooms) divided by land area; they differ only in what land is put in the denominator, and that is why quoting a density without saying which measure is being used is meaningless. Net residential density divides the dwelling units by the area of the residential lots alone — the land actually occupied by residential parcels, excluding street rights-of-way, parks, schools, open space, stormwater blocks, institutional and commercial sites and hazard lands. In the example, 1,300 units over 65 hectares gives 20.0 units per net hectare. Gross residential density divides the same dwelling units by the whole area of the residential neighbourhood, including the local streets, parks, schools, stormwater blocks and neighbourhood commercial that serve it: 1,300 units over 100 hectares gives 13.0 units per gross hectare.
| Measure | Denominator | Area (ha) | Density (units/ha) |
|---|---|---|---|
| Net residential density | Residential lots only | 65 | 20.0 |
| Gross residential density | Entire neighbourhood, including roads, parks, schools, stormwater | 100 | 13.0 |
| Ratio, net ÷ gross | — | — | 1.54 |
Net density is always the larger number, because it divides by a smaller denominator, and in Canadian suburbs the ratio is commonly between about 1.4 and 1.7 — roads alone typically take 20 to 25 per cent of a subdivision, and parks, schools and stormwater a further 8 to 15 per cent. Two cautions follow for practice. First, jurisdictions differ on the treatment of the half right-of-way abutting a lot, of local commercial, and of the school block, so the same subdivision can be honestly reported at several densities; a policy that sets a density target must define its own denominator, or it is unenforceable. Second, gross density is the measure that should be used for infrastructure and transit planning, because pipes, roads and buses serve the whole area including its streets, whereas net density is the measure that governs lot standards and built form. Density can equally be measured in persons per hectare, obtained by multiplying units per hectare by persons per unit — at 2.7 persons per unit the example yields 54 persons per net hectare and 35.1 per gross hectare, the latter being just at the lower bound of transit-supportive density.
The three densities answer three different planning questions, which is why all three are collected. Population density (residents per hectare) drives everything sized to people: water demand and wastewater generation, school pupil yield and site requirements, parkland standards expressed in hectares per thousand residents, library and recreation catchments, emergency-response staffing, retail support thresholds, and above all transit viability, since ridership depends on how many people are within walking distance of a stop. Employment density (jobs per hectare) drives the transportation system in the opposite direction: it determines peak-hour trip attraction, the directionality of the network, parking demand, and whether a corridor can support all-day two-way transit rather than one-way commuter service. Compared with population density it also measures the jobs-to-housing balance of a district, which is what determines commute length across a region and is a core economic-development indicator. Building density — floor space index, site coverage, and height — measures the intensity of construction on the land irrespective of what is inside it. This is what zoning can actually regulate, what determines shadow, wind and street enclosure, what infrastructure loading is derived from, and what fixes the development capacity and therefore the value of a site.
For downtown development projects in larger cities the appropriate measure is the floor space index (FSI, also called floor area ratio or FAR): the total gross floor area of all buildings on a site divided by the site area. A 4,000 square-metre downtown site carrying 60,000 square metres of gross floor area has an FSI of 15.0. FSI is the right instrument downtown for three reasons. First, downtown development is mixed-use — office, retail, hotel, institutional and residential in one building — so dwelling units per hectare describes only part of the project and understates a tower whose lower twenty floors are offices. Second, FSI measures what is built rather than how it is occupied, so it remains valid when a floor converts from office to residential. Third, it is the currency of the tools downtown zoning actually uses: density bonusing, in which additional FSI is exchanged for public benefit; transfer of development rights from a heritage site; and the negotiation of community amenity contributions. FSI is used together with, not instead of, height limits, site coverage, setbacks and angular planes, since the same FSI can be delivered as a slab or a point tower with entirely different effects on the street. For transportation and servicing analysis downtown, the complementary measure is residents plus jobs per hectare, which is the density figure that rapid-transit planning is calibrated against.
