ACUITY BRANDS, INC. AMENDED AND RESTATED SEVERANCE AGREEMENT

Exhibit 10(iii)A(46)

ACUITY BRANDS, INC.

AMENDED AND RESTATED SEVERANCE AGREEMENT

THIS AMENDED AND RESTATED AGREEMENT (the “Agreement”), made and entered into as of this 1st day of August, 2005, by and between ACUITY BRANDS, INC., a Delaware corporation (the “Company”), and John K. Morgan (the “Executive”).

W I T N E S S E T H:

WHEREAS, Executive is a key employee of the Company and an integral part of the Company’s management; and

WHEREAS, the Company desires to provide the Executive with certain benefits if the Executive’s employment is terminated under certain circumstances; and

WHEREAS, the Company and the Executive entered into an Amended and Restated Severance Agreement, dated as of January 20, 2004, which the parties now desire to amend and restate as hereinafter provided; and

WHEREAS, the Company and the Executive have determined that it is in their mutual best interests to enter into this amended and restated Agreement;

NOW, THEREFORE, the parties hereby agree as follows:

Unless earlier terminated as hereinafter provided, this Agreement shall commence on the date hereof and shall be for a rolling, two-year term (the “Term”) and shall be deemed to extend automatically, without further action by either the Company or Executive, each day for an additional day, such that the remaining term of the Agreement shall continue to be two years; provided, however, that either party may, by written notice to the other, cause this Agreement to cease to extend automatically and, upon such notice, the “Term” of this Agreement shall be the two-year period following the date of such notice and this Agreement shall terminate upon the expiration of such Term. This Agreement shall not be considered an employment agreement and in no way guarantees Executive the right to continue in the employment of the Company or its affiliates. Executive’s employment is considered employment at will, subject to Executive’s right to receive payments and benefits upon certain terminations of employment as provided below.

As of the date hereof, this Agreement is intended to, and shall, supersede and replace in their entirety the severance benefits provided under Executive’s Amended and Restated Severance Agreement, dated as of January 20, 2004.

2.1 “ Board ” or “ Board of Directors ” — The Board of Directors of Acuity Brands, Inc., or its successor.

2.2 “ Cause ” — The involuntary termination of Executive by the Company for the following reasons shall constitute a termination for Cause:

(a) If termination shall have been the result of an act or acts by the Executive which have resulted in a conviction by an applicable court of law of a felony (other than traffic-related offenses);

(b) If termination shall have been the result of an act or acts by the Executive which are in the good faith judgment of the Board to be in violation of law or of written policies of the Company and which result in material injury to the Company;

(c) If termination shall have been the result of an act or acts of dishonesty by the Executive resulting or intended to result directly or indirectly in gain or personal enrichment to the Executive at the expense of the Company; or

(d) Upon the continued failure by the Executive substantially to perform the duties reasonably assigned to Executive given Executive’s training and experience (other than any such failure resulting from incapacity due to mental or physical illness not constituting a Disability, as defined herein), after a demand in writing for substantial performance of such duties is delivered by the Board, which demand specifically identifies the manner in which the Company believes that the Executive has not substantially performed his duties, and such failure results in material injury to the Company.

If, in the reasonable good faith judgment of the Board, the events giving rise to the termination for Cause are curable, Executive shall have a period of thirty (30) days from delivery of notice by the Board of such act or acts within which to cure.

2.3 “ Company ” — Acuity Brands, Inc., a Delaware corporation, or any successor to its business and/or assets.

2.4 “ Date of Termination ” — The date specified in the Notice of Termination (which may be immediate) as the date upon which the Executive’s employment with the Company is to cease.

2.5 “ Disability ” — Disability shall have the meaning ascribed to such term in the Company’s long-term disability plan or policy covering the Executive, or in the absence of

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such plan or policy, a meaning consistent with Section 22(e)(3) of the Internal Revenue Code of 1986, as amended.

2.6 “ Good Reason ”. A “Good Reason” for termination by Executive of Executive’s employment with the Company shall mean the occurrence during the Term (without Executive’s express consent) of any of the following acts by the Company, or failures by the Company to act, and such act or failure to act has not been corrected within thirty (30) days after written notice of such act, or failure to act, is given by Executive to the Company:

(a) a change in Executive’s title of President and Chief Executive Officer of Acuity Lighting Group or Executive Vice President of the Company or a material adverse change in Executive’s duties and responsibilities;

(b) the relocation of the principal office where Executive is required to work to a location more than fifty (50) miles from the City of Atlanta, Georgia (i) for more than six (6) months, or (ii) if for less than six (6) months, without providing for Executive to travel to and from Atlanta, Georgia on a periodic basis at the Company’s expense;

(c) a reduction in base salary and target bonus opportunity (not the bonus actually earned) below the level in effect on the date of this Agreement, unless such reduction is consistent with reductions being made at the same time for other executive officers of the Company;

(d) a material reduction in the aggregate benefits provided to Executive by the Company under its “employee benefits plans”, as defined in Section 3(3) of ERISA (“Company Employee Benefit Plans”), on the date of this Agreement, except in connection with a reduction in such benefits which is consistent with reductions being made at the same time for other executive officers of the Company;

(e) an insolvency or bankruptcy filing by the Company; or

(f) a material breach by the Company of this Agreement.

2.7 “ Notice of Termination ” — A written notice from one party to the other party specifying the Date of Termination and which sets forth in reasonable detail the facts and circumstances relating to the basis for termination of Executive’s employment.

2.8 “ Severance Period ” — A period equal to the lesser of (i) twenty-four (24) months from the Executive’s Date of Termination or (ii) the number of months (rounded to the nearest month) from the Executive’s Date of Termination until the date he attains age 65; provided, however, that the Severance Period shall in no event be less than six (6) months.

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2.9 “ Severance Protection Agreement ” — An agreement between Executive and the Company providing for the payment of compensation and benefits to Executive in the event of Executive’s termination of employment under certain circumstances following a “change in control” of the Company (as defined in such agreement).

This Agreement provides for the payment of compensation and benefits to Executive in the event his employment (i) is involuntarily terminated by the Company without Cause, or (ii) is terminated by Executive for Good Reason. If Executive is terminated by the Company for Cause, dies, incurs a Disability or voluntarily terminates employment (other than for Good Reason), this Agreement shall terminate, and Executive shall be entitled to no payments of compensation or benefits pursuant to the terms of this Agreement; provided, that in such events, Executive shall be subject to the restrictive covenants set forth in the letter agreement, dated August 1, 2005, between the Company and Executive and not the Restrictive Covenants set forth in Section 5 below; provided, further, that in such events, Executive will be entitled to whatever benefits are payable pursuant to the terms of any health, life insurance, disability, welfare (except for a severance plan or program), retirement, deferred compensation, or other plan or program maintained by the Company.

If, as a result of Executive’s termination of employment, Executive becomes entitled to compensation and benefits under this Agreement and under a Severance Protection Agreement, Executive shall be entitled to receive benefits under whichever agreement provides Executive the greater aggregate compensation and benefits (and not under the other agreement) and there shall be no duplication of benefits.

If Executive’s employment is involuntarily terminated by the Company during the term of this Agreement without Cause (and such termination does not arise as a result of Executive’s death or Disability) or if Executive terminates his employment for Good Reason, Executive shall be entitled to the compensation and benefits provided for below, provided that Executive, as provided for in Section 4.10, executes a release of claims substantially in the form attached hereto as Exhibit A. In the event Executive is terminated without Cause or Executive terminates his employment for Good Reason, the Compensation Committee of the Board of Directors may, in its discretion and to provide equitable treatment, grant benefits to Executive in addition to those provided below in circumstances where Executive suffers a diminution of projected benefits as a result of Executive’s termination prior to attainment of age 65, including without limitation, additional retirement benefits and acceleration of long-term incentive awards.

4.1 Base Salary . Executive shall continue to receive his Base Salary (subject to withholding of all applicable taxes) for the entire Severance Period (as defined in Section 2.8

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above), payable in the same manner as it was being paid on his Date of Termination. In the event of Executive’s death prior to the end of the Severance Period, the payments of Base Salary shall cease.

4.2 Annual Bonus . Executive shall be paid a bonus in an amount equal to the greater of (i) the annual incentive bonus that would be paid or payable to Executive for the fiscal year of the Company during which Executive’s Date of Termination occurs under the Company’s annual incentive plan (“Incentive Plan”), assuming the target level(s) of performance had been met for such fiscal year, multiplied by a fraction (the “Pro Rata Fraction”), the numerator of which is the number of days that have elapsed in the then current fiscal year through Executive’s Date of Termination and the denominator of which is 365, or (ii) the annual incentive bonus that would be paid or payable to Executive for the fiscal year of the Company during which Executive’s Date of Termination occurs under the Incentive Plan based upon the Company’s actual performance for such fiscal year, multiplied by the Pro Rata Factor. The bonus amount determined pursuant to Section 4.2(i) shall be paid to Executive within ten (10) days of Executive’s Date of Termination and any additional amount payable pursuant to Section 4.2(ii) shall be payable at the same time as bonuses are payable to other executive under the Incentive Plan.

4.3 Stock Options . Unvested Stock Options granted to Executive under the Acuity Brands, Inc. Long-Term Incentive Plan (“LTIP”) shall continue to vest during the Severance Period, provided, that if Executive dies during the Severance Period, the continued vesting of such Stock Options shall cease. Stock Options vested as of Executive’s Date of Termination and Stock Options that vest during the Severance Period shall remain exercisable for the shorter of the remaining exercise term or the length of the Severance Period. Subject to the proviso at the end of this sentence, all Stock Options outstanding at the end of the Severance Period shall be immediately forfeited; provided, that if the Stock Option Agreement granting the Stock Option to Executive provides for more favorable continued vesting or exercisability after Executive’s Date of Termination, the provisions of such Stock Option Agreement shall apply to the vesting and exercisability of Executive’s Stock Options after Executive’s termination.

4.4 Restricted Stock . Any performance-based Restricted Stock granted to Executive under the LTIP for which the specific performance targets have been achieved and a Vesting Start Date (as defined in the agreement granting the Restricted Stock to Executive, the “Restricted Stock Agreement”) has been established as of Executive’s Date of Termination, shall become fully vested and nonforfeitable as of Executive’s Date of Termination. Performance-based Restricted Stock for which the specific performance targets are achieved and a Vesting Start Date is established during the Severance Period shall continue to vest during the Severance Period. If Executive dies during the Severance Period, any performance-based Restricted Stock for which a Vesting Start Date has been established during the Severance Period shall become fully vested and nonforfeitable and the Restricted Stock for which a Vesting State Date has not been established shall be forfeited. The Vested Value (as defined in the performance-based Restricted Stock Agreement) of the shares of Restricted Stock vesting pursuant to this Section 4.4 shall be delivered to Executive in the

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manner provided in the Restricted Stock Agreement within ten (10) days of the vesting date, using the vesting date as the date for determining the Vested Value.

Any Restricted Stock granted to Executive under the LTIP that is not performance-based shall be subject to accelerated vesting and shall vest each month during the Severance Period on a monthly pro rata basis calculated from the date of grant to the end of the Severance Period, provided, that if Executive dies during the Severance Period, the continued vesting shall cease and any such unvested Restricted Stock shall be forfeited.

Subject to the proviso at the end of this sentence, all Restricted Stock that has not vested at the Termination Date or during the Severance Period shall be immediately forfeited at the end of the Severance Period; provided, that if the Restricted Stock Agreement granting the Restricted Stock to Executive provides for more favorable continued vesting after Executive’s Date of Termination than provided in this section, the provisions of such Restricted Stock Agreement shall apply to the vesting of Executive’s Restricted Stock after Executive’s termination.

4.5 Supplemental Executive Retirement Plan . Executive shall continue to accrue credited service under the 2002 Supplemental Executive Retirement Plan during the Severance Period.

4.6 Supplemental Deferred Savings Plan . Company contributions credited to Executive’s Matching and Supplemental Subaccounts under the Supplemental Deferred Savings Plan (“SDSP”) shall become 100% vested and nonforfeitable as of Executive’s Date of Termination and shall be distributed from the SDSP at the end of the Severance Period.

4.7 Health Care, Life Insurance and Long-Term Disability Coverages . The health care (including dental and vision coverage, if applicable), term life insurance and long-term disability coverages provided to Executive at his Date of Termination shall be continued at the same level as for active executives and in the same manner as if his employment had not terminated, beginning on the Date of Termination and ending on the last day of the Severance Period. Any additional coverages Executive had at termination, including dependent coverage, will also be continued for such period on the same terms, to the extent permitted by the applicable policies or contracts. Any costs Executive was paying for such coverages at the time of termination shall be paid by Executive by separate check payable to the Company each month in advance or, at Executive’s election, may be deducted from his Base Salary payments under Section 4.1. If the terms of any benefit plan referred to in this Section, or the laws applicable to such plan do not permit continued participation by Executive, then the Company will arrange for other coverage(s) satisfactory to Executive at Company’s expense which provides substantially similar benefits or, at Executive’s election, will pay Executive a lump sum amount equal to the annual costs of such coverage(s) for the Severance Period. A benefit provided under this Section 4.7 shall cease if Executive obtains other employment and, as a result of such employment, health care, life insurance or long-term disability benefits are available to Executive.

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4.8 Outplacement Services . Executive will be provided with customary outplacement services by an outplacement firm selected by the Company for the Severance Period, provided that the Company’s total cost for such services shall not exceed an amount equal to ten percent (10%) of Executive’s Base Salary.

4.9 Other Benefits . Except as expressly provided herein, all other fringe benefits provided to Executive as an active employee of the Company (e.g., 401(k) plan, AD&D, car allowance, club dues, etc.), shall cease on his Date of Termination, provided that any conversion or extension rights applicable to such benefits shall be made available to Executive at his Date of Termination or when such coverages otherwise cease at the end of the Severance Period. Except as expressly provided herein, for all other plans sponsored by the Company, the Executive’s employment shall be treated as terminated